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Monographs on Industrial Chemistry

THE ZINC INDUSTRY

ERNEST A, SMITH

MONOGRAPHS ON INDUSTRIAL
CHEMISTRY

Edited by Sir EDWARD THORPE, C.B., LL.D., F.R.S.

Emeritus Professor of General Chemistry in the Imperial College of Science and Technology,
South Kensington ; and formerly Principal of the Government Laboratory, London.

INTRODUCTION

TOURING the last four or five decades the Appli-
*-* cations of Chemistry have experienced an extra-
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of another ; an obscure phenomenon like Catalysis is
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MONOGRAPHS ON INDUSTRIAL CHEMISTRY
EDITED BY SIR EDWARD THORPE, C.B., LL.D., F.R S.

THE ZINC INDUSTRY

ERNEST A. SMITH, Assoc.R.S.M.,

Deputy Assay- Master \ Sheffield ; Formerly of the Metallurgical

Department of the Royal School of Mines, London :

Member of the Institution of Mining and

Metallurgy ; Member of the Institute

of Metals ; Member of the

Society of Chemical

Industry

WITH 4 PLATES, AND DIAGRAMS IN THE TEXT

LONGMANS, GREEN AND CO
39 PATERNOSTER ROW, LONDON

FOURTH AVENUE AND JOTH STREET, NEW YORK
BO(MBAY, CALCUTTA, AND MADRAS

PREFACE

ALTHOUGH the art of zinc extraction has been practised in
this country for more than a century, comparatively little has
been written relative to its development since the publication
of the classical work of Dr. John Percy, which appeared in 1861.

It is probably this absence of a special literature dealing with
the position of the zinc industry in recent years that partly
accounts for the lack of interest hitherto shown in this branch
of British metallurgy.

At the present time, however, the importance of the production
of zinc and other non-ferrous metals is, fortunately for this country,
becoming more generally recognised ; it is, therefore, in the
highest degree desirable that there should be available treatises
suitable for the use of those interested in non-ferrous metals,
whether they are manufacturers, users of metals, scientific
investigators, or students of metallurgy.

In this work the author has endeavoured to give a general
survey of the development of the zinc industry, and its present
and possible future position in relation to the various metal
industries of this country.

In its preparation the author has freely availed him-
self of the current literature on the subject. He would more
particularly express his indebtedness to the papers by J. C.
Moulden, on " Zinc, its Production and Industrial Applications "
(Royal Society of Arts, 1916) ; H. M. Ridge, " The Utilisation
of the Sulphur Contents of Zinc Ore " ; and also to the Bulletin
of the Imperial Institute, 1915-1916, for useful information on
the zinc ore resources.

384941

PREFACE

Thanks are also due to Mr. Ridge for valuable information
and for kindly providing the illustrations of the roasting furnaces,
and to Dr. F. C. Thompson for preparing the photomicrographs.

With regard to statistics the figures for the year 1913 have
been given purposely in preference to those of subsequent years,
as being more representative of the zinc industry under normal
conditions. In many cases later figures are not procurable, some
of the belligerent nations having ceased to issue them since 1914.
Due consideration has, however, been given to the very marked
influence of the war on the zinc industry.

A bibliography of some of the more important publications
relating to the subject is appended.

CONTENTS

PAGE

PREFACE v

INTRODUCTION i

Position of Zinc in Commerce and in the Arts ... . . 4

CHAPTER I.
THE HISTORY OF ZINC 7

CHAPTER II.

THE RISE AND PROGRESS OF THE PRODUCTION OF ZINC . . 10

The Establishment of Zinc Smelting Centres 10

The Development of the British Zinc Industry 18

British Empire Centres of Zinc Production 29

The Development of the European Zinc Industry .... 33

The Development of the American Zinc Industry .... 40

Zinc Production in Asia 43

CHAPTER III.

ZINC ORES AND THEIR SOURCES OF SUPPLY 46

Zinc Ores : Their Nature, Occurrence and Distribution . . . 46

Zinc Ores in the British Empire 51

European Sources of Zinc Ores 55

American Sources of Zinc Ores 61

Asiatic Sources of Zinc Ores 67

CHAPTER IV.

THE MARKETING OF ZINC ORES 70

The Concentration of Zinc Ores 70

The Valuation of Zinc Ores 73

The European Ore Trade 77

CHAPTER V.

THE SMELTING OF ZINC ORES 79

Recent Advances in Zinc Smelting 104

CHAPTER VI.

ZINC SMELTING — (Continued) in

By-products in the Smelting of Zinc in

Sulphuric Acid in

The Cost of Zinc Production 119

The Conditions of Labour in Zinc Smelting 122

CHAPTER VII.

OTHER METHODS OF ZINC PRODUCTION 124

The Electric Smelting of Zinc Ores . . . * . . . 124
Hydro-metallurgical Processes of Zinc Production . . . .130

vii

CONTENTS

CHAPTER VIII.

PAGE

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC . . . 137
The Micro-structure of Zinc ......... 14°

Impurities in Commercial Zinc ........ M5

CHAPTER IX.

THE MARKETING OF ZINC . . . ...... *4&

Grades of Commercial Zinc . ........ M8

The Price of Zinc ........... X5*

The World's Zinc Markets . ........ *54

The Spelter Convention *; J .' | • .>:X •* S * ^H* ' • X55
The Production and Consumption of Zinc ...... 157

CHAPTER X.

THE INDUSTRIAL APPLICATIONS OF ZINC ...... 161

Rolled or Sheet Zinc . ........ 166

ZincCastings . ... .5^* . . ,. . .> ....... • • 167

Other Uses of Zinc . ... '•'"..' . , . . • • -

Zinc Dust (Blue Powder) . .... » . . • •

CHAPTER XI.
INDUSTRIAL ZINC ALLOYS ; M. . • . ': ' . .

CHAPTER XII.
COMMERCIAL COMPOUNDS OF ZINC: ZINC PIGMENTS .... 19*

CHAPTER XIII.

THE FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN . .198

BIBLIOGRAPHY . . . i. . .^ . . . . • • 213

INDEX . . . . . . ^ . . ^ . . - 223

LIST OF PLATES

PLATE To face page

I. PHOTOMICROGRAPH OF CAST ZINC . ., ;. . .| x.2

DITTO, SHOWING TWINING . ., . . ,: > ./
II. PHOTOMICROGRAPH OF CAST ZINC WITH 30% OF LEAD 144

III. BRASS (70% COPPER, 30% ZINC) AS CAST, SHOWINGN

CORD STRUCTURE . . Beiween pp..

IV. BRASS (70% COPPER, 30% ZINC) AFTER ANNEALING)- 144-145

FOR ONE HOUR AT 750° C., SHOWING CRYSTAL-
LINE STRUCTURE /

viii

THE ZINC INDUSTRY

INTRODUCTION

THERE is considerable truth in the statement, made more than
sixty years ago by Dr. John Percy,1 the father of British metal-
lurgy, that " in proportion to the success with which the metal-
lurgic art is practised in this country will the interests of the
whole population, directly or indirectly, in no inconsiderable
degree be promoted." This is true, not only of the United
Kingdom, but also of the British Empire.

Had the importance of this fact been more fully recog-
nised during the past three or four decades by the Government
and by those engaged in the mining and metallurgical industries,
there can be little doubt that the valuable mineral resources
of the Empire would have been more fully developed and
utilised, and adequate provision would have been made for smelt-
ing the ores within the Empire in the interests of the metal
industries of this country and the Colonies. The crisis through
which we are passing has revealed to what an extent our lack
of metallurgical enterprise has enabled Teutonic influence to
gain control of the mineral and metal resources of the British
Empire, and made the United Kingdom largely dependent on
foreign supplies to meet her increasing demands for industrial
metals.

" Before the war the world's markets for the majority of the
non-ferrous metals were very largely controlled by a group of

1 Inaugural lecture to students of the Royal School of Mines, London,
1851.

I B

NDUSTR Y

German metal companies engaged primarily in buying metals
and acting as selling agents for producers.

" How complete this control was few people knew.
" The outbreak of war disclosed it in all its formidableness.
"The most important of these concerns was the Metallgesell-
schaft of Frankfort-on-the-Main. This place was the centre of
certain German financial interests which had combined to
establish the Metall Bank and the Metallurgische Gesellschaft.
In one way or another this great organisation had established
financial interests in metal undertakings, not only in Germany
and Austria, but also in the United States of America, the United
Kingdom, and various parts of the British Empire.

" This enormously powerful group of companies controlled the
world's metal markets, of which Frankfort became the centre.

'* Their connections with other undertakings and their ramifica-
tions were exceedingly complicated and difficult to control.
In some instances there was a direct financial connection ; in
others the connection was established by some form of agree-
ment. But whatever the method, there was no doubt about
the ascendency acquired by the Germans."1

In no case was this control more stringent than in that
of zinc. Before the war the Germans, by means of the so-called
Zinc Convention which they organised, were placed very
largely in control of the zinc trade of the world, and were also
able to enter into long-date contracts for the supply of large
quantities of ore mined within the British Empire, thus placing
British consumers of zinc in an unwarrantable position of in-
security.

This control was a source of great embarrassment to the
British Government at the outbreak of war, and for quite two
years afterwards the cause of this country and its Allies was
severely handicapped because we were without the necessary
metal supplies, and many trades were in jeopardy. With the
view of preventing this control in the future, the Government
has recently passed the " Non-ferrous Metals Bill," which is a
measure designed to keep the control of the supply of these
essential metals in British hands.

For many years the United Kingdom has had to depend on
imported metal to the extent of more than 70 per cent, of her
zinc requirements.

1 H. C. H. Carpenter, Nature, 1917, vol. c., p. 284.
2

INTRODUCTION

Before the war the bulk of the British supply of zinc was
obtained from Germany and Belgium. Each country was a
large producer of the metal, and each also a large importer
of zinc ore from the most important zinc mine in the British
Empire, that at Broken Hill, in Australia.

The outbreak of war led to a remarkable situation in the
British and Colonial zinc markets, owing to the sudden cutting
off of pre-war supplies of the metal, and the loss to Australia
of nearly all her markets for zinc ore (concentrates). The
demand for the metal increased enormously, zinc as a con-
stituent of cartridge brass being an indispensable munition metal.
But whilst there were enormous quantities of zinc ore await-
ing shipment in New South Wales, most of the British smelters
were unable to treat it, as their furnaces were not adapted to
this particular class of ore.

Consequently, at the outbreak of war Great Britain found
herself in the anomalous position of having command of the
seas, and with an immense supply of zinc ore within the Empire,
but with smelting plant quite inadequate to convert this ore into
metal.

The serious shortage of spelter was temporarily met by exports
from the United States, the world's largest producer of zinc, but
as the production in that country is usually only about equal to
the consumption, the result was a rapid rise in the price of the
metal, the selling price appreciating to more than five times its
pre-war figure.

These conditions led to an inquiry into the position of the
British zinc industry, and also to a consideration of the possi-
bilities of so increasing the future output of metal that it shall
at least be sufficient to meet all home requirements. Such a
situation as that in which Great Britain found herself at the
beginning of hostilities should never have been allowed to arise,
and it is satisfactory to know that steps are being taken to make
its recurrence impossible. There is every reason why the supplies
of zinc concentrates which have hitherto been largely shipped
to the Continent, should be treated within the British Empire,
and it is to be hoped that in the future this will be done.
Legislation has decided that the resources of the Empire are
not, in the future, to be left to be exploited by Germans.

As showing the great importance of the Broken Hill zinc ore
deposits it may be stated that the output would be more than

3 B 2

THE ZINC INDUSTRY

sufficient to supply the entire demand of the United Kingdom
for metallic zinc.

With the view of relieving the zinc situation and rendering
the United Kingdom less dependent on foreign supplies, important
schemes, which are dealt with later in this monograph, have been
taken in hand, and there seems to be some prospect that the
British zinc smelting industry will, in the near future, take the
position that its importance demands.

Steady progress has already been made, and the movement is
progressing at an accelerated rate, largely through the impetus
given to it by the crisis through which the country is now passing.

When the rank this country holds among nations as regards
her metal industries is taken into consideration, it must be
a matter of surprise that in the past so little attempt appears
to have been made to develop the zinc smelting industry
so that the production of this important industrial metal shall
be commensurate with the needs of the country.

The Position of Zinc in Commerce and in the Arts

Although zinc was extracted from its ores on a commercial
scale in Europe in the middle of the eighteenth century, it did
not begin to take a prominent place in the arts until a
century later, so that, from an industrial point of view, it is
regarded as a comparatively modern metal when compared with
metals such as lead and copper that have been in common use
for centuries.

Zinc, or spelter, as it is termed commercially, possesses physical
and chemical properties that render it extremely useful, and
when these properties were fully recognised the metal rose,
somewhat rapidly, to a position of considerable importance.
It now occupies the third place in the list of non-ferrous base
metals of value in the metal industries, only being surpassed in
this respect by lead and copper.

The rapidity with which zinc has grown in industrial importance
may be judged from the fact that the world's output has almost
quadrupled itself in the past thirty years, and in that time the
British production has increased tenfold. The world's produc-
tion of the three non-ferrous metals in most common use in the
years 1911-1913 — the latest figures available under normal
conditions — was as follows : —

INTRODUCTION

WORLD'S OUTPUT OF NON-FERROUS METALS. l
(In metric tons. 2204-6 Ib.)

Production. Consumption.
Metric tons. Metric tons.

Average
Price.

1911.
Lead
Copper
Zinc

1,136,000
893,800
902,100

1,149,200
954,100
911,400

£ s- d.
13 9 2

56 i 9
25 3 2

1912.
Lead
Copper
Zinc

1,181,800
1,018,600
977,900

1,201,800
1,038,700
996,900

17 15 10
73 i 2
26 3 4

1913-
Lead
Copper
Zinc

1,186,700
1,005,900
997,900

1,196,200
1,044,500
1,012,700

18 6 2

68 5 9
22 14 3

From the figures for the production in 1913 it will be seen
that for every 1,000 tons of lead produced there were 921 tons of
copper and 920 tons of zinc.

This close coincidence between the figures for copper and zinc
shows that the relative position occupied by zinc in the arts and
commerce was, at the outbreak of war, practically the same as
that of copper, a metal which has been in use for industrial
purposes for a very much longer period.

Owing to the disturbance caused by the war, it is doubtful
how far this ratio is to-day strictly preserved.

Zinc owes its important position largely to its valuable pro-
perty of preventing the corrosion or rusting of iron when this
metal is coated superficially with it, and also to the fact that
it is a valuable constituent of brass, now one of the most
widely used industrial alloys.

It may be well here to point out that the nomenclature of zinc
is a little confusing. The British usage, and also to a certain
extent the American, is to apply the term " spelter " to designate
the ordinary ingot zinc of commerce, the word " zinc " being
usually reserved for the rolled metal and for chemical and
mineralogical terminology.

1 Statistics issued by the Metall Gesellschaft and the Metall Bank of
Frankf ort-on-the-Main .

THE ZINC INDUSTRY

The miner sells ore to the smelter on the basis of its zinc
content, and the latter markets the extracted metal as spelter,
which is not " a metal " in sensu stricto, but a commercial
alloy produced by the smelting of zinc ores, and, although
consisting mainly of zinc, usually contains sensible proportions
of lead and other metals.

Recent usage, so far as Great Britain is concerned, has inclined
towards the use of the word spelter for all grades of metal up to
those containing 99-8 per cent, of zinc or thereabouts, those of
higher quality than this being designated " fine-zinc." l Although
arbitrary, there are commercial reasons for the distinction.

The crude zinc obtained direct from ores by smelting is usually
known in the trade as " virgin spelter " in this country, and as
" primary zinc " in America, whereas metal that has been in use
and then remelted is termed " remelted spelter " in this country
and " secondary zinc " in America.

The term " hard spelter " is given to a cheap and common
brand of metal, consisting of zinc contaminated with iron,
resulting from the galvanising process.

1 " Zinc, its Production and Industrial Applications," F. C. Moulden.
Journ. Roy. Soc. of Arts, 1916, vol. Ixiv, p. 500.

CHAPTER I

THE HISTORY OF ZINC

IN turning to the history of zinc it is difficult to determine
when, and by whom, the metal was first isolated in the metallic
state. Primitive metallurgical processes are referred to in the
oldest known historical records, but none of the descriptions
of ores and processes used, and of metals obtained, can be applied
with any degree of certainty to metallic zinc. Undoubtedly
zinc as a distinct metal was unknown in early times, in fact as
late as the sixteenth century it was not known in Europe ; but
there are strong reasons for the belief that the Chinese were
acquainted with it as metal at least several centuries earlier.1

In Roman times it was known in the alloyed state as a con-
stituent of brass, an alloy of zinc and copper.

Zinc first appears in the coins of the Republic as an impurity ;
as an intentional addition, however, it only dates from the time
of Augustus (20 B.C. to 14 A.D.), when brass was made for the
first time in the world's history.

The Romans were the first makers of brass. Although they
were unacquainted with the essential constituent, zinc, yet they
had discovered that, by melting copper together with a certain
ore (calamine, the natural zinc carbonate) by the process known
as " cementation," a yellow alloy of a more golden colour than
bronze could be obtained, the alloy being known subsequently
as " calamine brass." That the Romans were the first inventors
of brass is, according to Prof. Gowland,2 without doubt, as the
alloy is not found in Greece or the Greek colonies or elsewhere
until the time of the Roman Empire.

1 W. Gowland, Presidential Address, Journ. Inst. of Metals, 1912,
vol. vii, p. 42.

2 Loc. cit., p. 46.

THE ZINC INDUSTRY

The first mention of zinc as a distinct metal is usually ascribed
to the alchemist Paracelsus (1493-1541), but there appears to
be little doubt that it was first actually recognised in the metallic
state in Europe by his contemporary, Georgius Agricola, the
renowned metallurgical writer, who about the middle of the
sixteenth century accidentally discovered it in the wall crevices
of a smelting furnace treating zinciferous lead and copper ores
at Goslar in the Hartz.1

As, however, Agricola only describes the metal and makes no
mention of the extraction of zinc from its ores in his well known
work " De Re Metallica," 1556, it may be concluded that the
metal was not generally known in his time.

The discovery of zinc in Europe seems to have been quite
independent of any knowledge of the metal in the Far East,
where, as previously stated, it was undoubtedly known prior to
the sixteenth century.

There is also some evidence that zinc was known and extracted
in India prior to the sixteenth century.

The localities of Eastern production have never been
adequately investigated. Nevertheless, it is well known that
the Chinese have, from very early times, possessed considerable
metallurgical knowledge, and it is not improbable that when
the early history of the metallurgy of this ancient people
comes to be written it will be found that the first separa-
tion of metallic zinc from its ores must be attributed to the
Chinese.

There is evidence that the greater part of the zinc produced
in the sixteenth and the seventeenth centuries came from China.
The metal was imported from China into Europe by Portuguese
and Dutch merchants under such names as tutinag, and spiauter,
or spialter ; hence the word speltrum, introduced by Boyle,
and the English word spelter, which is almost the only term for
crude zinc in the works at the present day.

The importation of zinc from China has continued to the
present day, and quite a substantial quantity of Chinese zinc
of very good quality has found its way to England since the war
began .

The earliest certain descriptions of zinc production in India

1 For full discussion of the early history of zinc, see Agricola's " DeRe
Metallica," transited by H. C. and L. H. Hoover, London, 1912,
pp. 408-410.

THE HISTORY OF ZINC

appear to be some recipes for its extraction dating from the
eleventh to the fourteenth centuries quoted by Praphulla Chandra
Ray in his " History of Hindu Chemistry," London, 1902, p. 39.
The crude distillation of zinc was conducted in Rajputana as
late as the beginning of the nineteenth century, and the remains
of such smelting, in this and other districts of India, are said to
be very ancient.

CHAPTER II

THE RISE AND PROGRESS OF THE PRODUCTION

The Establishment of Zinc Smelting Centres

WHATEVER uncertainty there may be as to the antiquity of the
discovery of metallic zinc, there appears to be little doubt that
the art of extracting it from its ores by distillation was acquired
from the Far East and was introduced into Europe in the latter
part of the eighteenth century.

There is a tradition, recorded by Bergman, that an Englishman
visited China in the eighteenth century expressly to learn the
method of making zinc ; that he attained his object and returned
home in safety with the secret ; and that some time afterwards
works were erected at Bristol for the extraction of zinc in large
crucibles by distillation per descensum} This tradition is sup-
ported by the fact that zinc works were established at Bristol
about 1740, by John Champion, who was, so far as is known,
the founder of the British spelter industry, and also the first
metallurgist in Europe to extract zinc from its ores commer-
cially. Exactly what circumstances led Champion to start the
spelter industry at Bristol must be more or less a matter of
conjecture, but probably it was due to the fact that a calamine-
brass industry had been in existence in England for about a
century previously.

Formerly calamine, an important ore of zinc, was fairly
abundant in England and was employed in brass-making, and
was also exported as ballast to the Continent to be used for the
same purpose. It is recorded that calamine-brass works were
erected in Surrey about the middle of the seventeenth century.
Works were also established in Bristol about 1702, and after-

1 Quoted by J. Percy, " Metallurgy of Copper and Zinc," London, 1861,
p. 520.

THE RISE AND PROGRESS OF THE PRODUCTION

wards at Cheadle, in Staffordshire, about 1720. Later, works
were erected for the manufacture of ingot-brass at Smethwick,
Swansea, and Llanelly.

The smelting of zinc ores was continued at Bristol for nearly
one hundred years, when it was transferred to Swansea, which
possessing greater natural facilities for the development of the
industry, gradually became the most important centre of zinc
production in the United Kingdom.

The manufacture of brass by cementation was also carried
on in Europe in the eighteenth century, notably at Moresnet
in Belgium, and at Beuthen in Poland, at which places important
deposits of calamine (zinc carbonate) were worked. As the art
of zinc smelting gradually became known, it necessarily followed
that in course of time it should be introduced at these noted
European centres of brass-making. It was not, however, until
some fifty years after the establishment of the industry in
England that it was introduced on the Continent.

The manufacture was started in Germany about 1798 by
Johann Christian Ruberg, who probably learned it in England,
and began zinc distillation at the glass works of Wessola, near
Pless, in Poland.

Ruberg first adopted the method of distillation per descensum
as practised at Bristol, but he soon found that it was very
defective, and devised the system of treatment in horizontal
muffles of large capacity, known as the Silesian method. Ruberg
thus laid the foundation of what became, in later times, the
important Silesian zinc industry.

About the same time, zinc distillation from calamine was
also started at Dollach, in Carinthia, by Dillinger, by the method
practised at Bristol, but the works^ only remained in operation
for a comparatively few years.

The calamine deposits at Moresnet, in Belgium, passed in
1795 under the suzerainty of France, and it is stated that the
Government in granting a concession of mining rights to the
Abbe Dony, imposed on him the obligation to make such experi-
ments as would enable the calamine to be reduced to the metallic
state. Whatever truth there may be in this story, the introduc-
tion of zinc smelting into Belgium is to be credited to the Abbe
Dony, who, after many years of experimental work, appears
to have made the independent discovery of a method of zinc
distillation and to have established works at Liege in 1807.

THE ZINC INDUSTRY

These works formed the corner-stone of what became in later
times the world-famed Belgian zinc industry. They have for
many decades outlived the native supply of zinc ores on which,
with the presence of coal of the district, the industry originally
depended.

Subsequently, works were established at Moresnet, near
Aix-la-Chapelle, to smelt the important deposits occurring at
La Vieille Montagne, La Nouvelle Montagne, and Corfalie.

Dony's method of zinc extraction differed from that employed
in Great Britain and in Silesia. He distilled the calamine in a
number of small retorts set in a single furnace, thus constituting
the Belgian method, adopted by all the Beigian zinc works
erected later, and subsequently in England and elsewhere.
Dony reaped little benefit from his discovery ; he died a ruined
man in 1819, and his successor, M. Dominique Mosselmann,
who was admitted as Dony's partner in 1816, took over the
works. Although a man of great energy and capability,
Mosselmann had not brought about any noteworthy progress
in the zinc industry when he died in 1837, possibly because
up to that time no regular demand had been found for the
increasing output of this new commercial metal.

Mosselmann carried on the works until his death, when his
successors, in order to realise his estate, founded the celebrated
Societe de la Vieille Montagne, with a capital of 7,000,000 francs
(£280,000) .*

The growth of the company was at first very slow, and it was
only when Saint Paul de Sincay took over the management that
the works began to prosper rapidly.

By the middle of the nineteenth century the Belgian industry
had become firmly established, and was a formidable rival to
that of Germany in the amount of zinc produced annually.
Both Belgium and Germany adopted the method of zinc distil-
lation per ascensum, which proved to be more economical and
more satisfactory than distillation per descensum as used in
England.

The latter method, which was also carried on to a limited
extent in Carinthia and Hungary, was discarded in England
in favour of the former method about the year 1850.

Towards the latter half of the last century zinc smelting was
also started in Austria, Holland, Spain and France, but the

1 J. Gilbert, The Mining Journal, London, 1916, vol. cxiv, p. 480,

THE RISE AND PROGRESS OF THE PRODUCTION

industry in these countries has never grown to very large
proportions, the production, even at the present time, being
insufficient to satisfy their own requirements.

During the eighteenth century the growth of the European
zinc industry was comparatively slow, owing most probably to
the somewhat limited use of the metal at that time in the manu-
facture of brass. Although Emerson used metallic zinc for the
manufacture of brass in England as early as 1781, its use for
this purpose extended very slowly owing to the indifference,
and even hostility, displayed by the calamine-brass makers, who
averred that the metal produced brass inferior in quality to
that produced by cementation.

The long survival of this ancient process, after the discovery
of metallic zinc, and its production on a commercial scale, afford
a striking example of the conservatism characteristic of early
British metallurgy.

At the beginning of the nineteenth century it was found
to be possible to convert zinc into sheets by heating it to a
temperature between 100° C. and 150° C. and rolling it while
hot, thus breaking down the crystalline structure of the metal,
and rendering it malleable and ductile.

The credit of this discovery is due to Hobson and Sylvester,
of Sheffield, who in 1805 obtained a patent for "a method of
manufacturing the metal called zinc into wire and into vessels."
This discovery was of no little importance, as it enabled the
metal to be used for the manufacture of sheets for roofing
purposes, for which the higher priced metal, copper, had hitherto
been employed.

Very little advantage appears to have been taken of the
patent in this country. The Abbe Dony, however, laid down the
first rolling mills for sheet zinc production at Liege in 1812, and
since that time the manufacture of zinc sheets has been a very
important branch of the Belgian zinc industry.

The initial difficulties of finding a suitable outlet for the
increasing quantities of the zinc produced at the different
centres of production lasted over several decades.

As late as 1825 the association for fostering the Prussian
industry offered a prize for the discovery of a useful employment
of zinc, and this led to its use for ornamental purposes, as imitation
bronze for statues, lamps, pedestals, and for architectural
pieces, etc.

THE ZINC INDUSTRY

Further impetus was given to the zinc industry by the
employment of the metal for the manufacture of the so-called
11 galvanised " iron, the name given to sheet iron coated super-
ficially with zinc to prevent its corrosion when exposed to
atmospheric influences.

The term " galvanised " is said to have been first used,
improperly, in France and subsequently adopted in this country.

The galvanising process is effected by dipping the iron articles
into a bath of melted zinc, a patent for zincing iron in this way
being granted to H. W. Crawford in 1837.

The application of these two valuable properties of zinc
greatly extended its use for industrial purposes when once their
importance was fully realised.

It was not, however, until the middle of the nineteenth century
that the zinc industry began to be established on a sure footing
in Europe. In 1830, the total production of spelter in Europe
was less than 5,ooo tons, and in 1840, ten years later, the total
output had only reached a little more than 17,000 tons.

From this time onwards, however, there was a steady increase
in the production of the metal, until it eventually occupied third
place in the list of non-ferrous metals of industrial importance.
A notable increase in output occurred from about 1873, due to
the progress of galvanising.

Zinc smelting was not introduced into America until 1838,
in which year the metal was first produced experimentally in
the United States. Between the years 1841 and 1850 various
attempts were made to smelt the red oxide ore of New Jersey,
which is contaminated with willemite and franklinite in such a
way that a clean separation could not at that time be economi-
cally effected.

The attempts to produce metallic zinc were unsuccessful,
and attention was then directed to the recovery of the zinc as
oxide, and works for the manufacture of zinc oxide on a com-
mercial scale were erected in Jersey City in 1854.

The regular production of metallic zinc was not undertaken
until 1859, when J. Wharton started zinc smelting in muffle fur-
naces of the Belgian type, with Pennsylvanian anthracite as fuel.

By 1870, six works were producing zinc in the United States
at the rate of approximately 4,500 tons per annum, while the
works in New Jersey produced in addition about 13,000 tons of
zinc oxide.

THE RISE AND PROGRESS OF THE PRODUCTION

While at this time the American industry was only just becom-
ing established, the European industry had made considerable
progress, as shown by the following figures giving the approxi-
mate zinc output for the various countries of Europe in 1870 : —

Long tons.

Germany . . . . . . . . . . . . 56,000

Austria . . . . . . . . . . . . 3,ooo

Belgium . . . . . . . . . . . . 46,000

Great Britain (estimated) . . . . . . 10,000

France ,, . . . . . . . . 6,500

Spain ,, . . . . . . . . 6,500

Total European zinc production in 1870

128,000

This amount, with 4,500 tons of spelter produced in the United
States, makes a total of approximately 133,000 tons as the
world's zinc production in 1870. The production of the indi-
vidual countries in recent years is dealt with on page 158.

Attention must be directed to the fact that although domestic
ores were mined and smelted in Europe at this time, a by no
means inconsiderable quantity of imported zinc ore was also
smelted. Thus, the total annual production of the famous zinc
ore in the island of Sardinia was, in 1870, about 49,200 tons,
representing 16,900 tons of zinc ; this ore was chiefly exported
to Germany, Belgium, and the United Kingdom.

The enormous increase in the rate of production, and in the
demand for zinc since the year 1870, is well shown in the follow-
ing figures, which give the approximate output and consumption
of zinc, in English tons from 1870 to the outbreak of war, in
intervals of ten years.

European

American.

World's

production.

consumption.

Year.

English tons, 2,240 Ib.

1870 . • ;

128,000 4,500

133,000

1880 .

207,000 21,000

228,000

230,000

1890 . . — —

343.ooo

345,000

1900

310,000 58,000

368,000

474,000

1910

557,000*

247,000

804,000

820,000

1913

663,000*

315,000

982,000

997,000

Includes small amounts produced in Australia.
15

THE ZINC INDUSTRY

It will be seen that not only has there been an enormous
increase of production, especially during the present century,
but the ratio between the European and the American produc-
tion has altered, implying far-reaching economic changes in
regard to the supply and demand for zinc.

The increase in the world's supply of zinc from 1845
to 1913, in English tons, has been plotted graphically by
J. C. Moulden in the accompanying curve (page 17). Prior
to 1845, the statistics are not very trustworthy, and in any
case the tonnage was so small as to have little bearing upon the
metal in relation to the part it plays to-day in our commerce.
The curve indicates in a striking manner the ever-increasing
relative rate of production, a considerable advance being noted
about 1873, due to the progress of galvanising. With the
exception of a decrease in 1900 and 1908, there has been pro-
gressive output, the increase for 1900 to 1913 being very remark-
able. In the relatively short space of sixty-eight years the
world's output has increased about 3400 per cent. (Moulden).
The actual figures compiled by Moulden for the world's zinc
production for the period included in the curve 1845-1913 are
as follows (in English tons) :—

THE WORLD'S PRODUCTION OF ZiNC.1
From 1845 to 1913.

Year.

English tons of
2,240 Ib.

Year.

English tons of
2,240 Ib.

i845

29,000

1904

612,687

i855

70,000

1905

643,906

1865 98,000

1906 688,321

1875 166,000

1907 725,616

1885 294,000

1908 711,514

1890 342,000

1909 762,559

1895 406,000

1910 797»336

1900 471,460

1911 880,411

1901 508,422
1902 544, 1 93

1912
1913

955,398
985,142

1903 561,547

A significant feature of the zinc industry is its limitation to
the comparatively few smelting centres in Europe and America

1 Compiled by J. C. Moulden, Journal of the Royal Society of Arts, 1916,
vol. Ixiv, p. 527.

THE RISE AND PROGRESS OF THE PRODUCTION

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THE ZINC INDUSTRY

already mentioned, viz. : Silesia, Westphalia and Belgium on
the Continent ; Swansea, Birmingham, and more recently Durham
in England ; Kansas, Illinois and New Jersey in the United States.
In recent years, a zinc smelting plant, to which reference will
be made later, has been erected at Port Pirie in Australia.
These are the more important smelting centres contributing to
the world's supply of zinc, and to one or other of these centres
practically all zinc ores have, hitherto, been shipped for treat-
ment.

This localisation of the zinc industry is due to the necessity
for cheap fuel, the occurrence of good quality fireclay required
for the retorts used in smelting, and to the necessity of skilled
labour, whilst the climatic conditions must be suitable to the
trying conditions of the workers.

It has been found very difficult to install zinc smelting works
without close regard to these somewhat narrow factors ; in
regard to labour especially, it takes many years to train the
workers, whose skill and practical knowledge may be said to
result from environment and in this branch of operative metal-
lurgy to become almost hereditary.1

The main strength of the great centres of zinc production
to-day may be said to be their force of skilled labour.

It may not be without interest to trace briefly the development
of the zinc industry in each of the different centres of produc-
tion. This will conduce to a more thorough appreciation of the
relative positions of the individual localities in contributing to
the world's supply of zinc.

The Development of the British Zinc Industry

As the enterprise at Bristol that marked the beginning of zinc
production, not only in Great Britain, but also in Europe, was
unsupported by any important domestic deposits of zinc ore,
and was handicapped by methods of smelting inferior to those of
Belgium and Silesia, it gradually languished and eventually died
out about 1860.

Meanwhile, the well-known firm of Vivians had, in 1835,
erected zinc smelting works at Swansea in South Wales, around
which, as a nucleus, gradually grew the British zinc smelting
industry.

1 H. L. Sulman, Presidential Address. Transactions of the Institute of
Mining and Metallurgy, 1910-1911, vol. xx.

THE RISE AND PROGRESS OF THE PRODUCTION

As already indicated, the process of extracting the metal
first practised in this country differed very materially from
that adopted later in Belgium and Silesia. In the English
method of distillation per descensum, the zinc vapour was
drawn downwards from the bottom of the pot or crucible to
the condensing apparatus, whilst in the process per ascensum
as practised on the Continent the vapour of the metal passed
from the uppermost point of the retort or muffle to the con-
densing apparatus. The English method was conducted in
large crucibles heated in a furnace in many respects similar to
those used in glass works for the fusion and preparation of
glass. The method is said to have entailed only a comparatively
small expenditure of manual labour, but it involved a much
larger consumption of fuel than in either the Belgian or the
Silesian process, and on that account the English process
was superseded by the Continental methods of smelting
about 1850.

The extensive zinc smelting works erected near Swansea by
Mr. Hussey Vivian in 1835 are stated to have contained English,
Silesian and Belgian zinc furnaces, from which it would appear
that British zinc metallurgists were giving attention to the
Continental methods of zinc production some years before they
finally abandoned the English method in favour of the Belgian
and Silesian processes.

Percy states that in 1861 both the Silesian and Belgian methods
of distillation were in use at a large zinc smelting works in this
country producing about 100 tons of zinc weekly.

With the growth of the zinc industry, works for the pro-
duction of the metal were established at Llanelly, Wigan,
Wrexham, Sheffield, Birmingham and Bristol, but Swansea has
always been the principal centre of zinc production in Great
Britain and is still responsible for a large proportion of the
metal annually produced in this country.

The early statistics of zinc output in Great Britain are not
very trustworthy, but it would appear that prior to 1880 the
annual production was under 10,000 tons (English, 2,240 lb.).
Four years later the output was 30,000 tons, showing that the
production of the metal had increased threefold, due to the
progress of the galvanising industry.

Between 1884 and 1887 the output fell to 20,000 tons, and
then rose again rapidly to about 31,000 tons in 1889.

19 C 2

THE ZINC INDUSTRY

With the exception of a fall to 24,000 tons in 1896, the annual
production averaged about 30,000 tons between the years 1889
and 1901, from which date the output rapidly increased until
it reached approximately 50,000 tons in 1905. Since that
time the British production of zinc has fluctuated between 50,000
and 60,000 English tons annually.

The accompanying curve shows the approximate annual
output of zinc in Great Britain from 1875 to 1915 in metric
tons.

The growth of the British zinc industry is largely due to the
rapid progress in the manufacture of galvanised or zinc covered
sheets, which soon became an important branch of British
metallurgical industry, and created a demand for zinc which
became so considerable that the smelters in this country could
not keep pace with its constantly increasing requirements. This
presented the opportunity for the importation of foreign zinc,
an opportunity of which Continental smelters readily availed
themselves, with the result that very considerable quantities of
metal have for some years been shipped to this country annually,
chiefly from Belgium and Germany, a condition of things that
must have been very helpful to the development of the zinc
industry in those countries. The extent of this importation of
foreign zinc to meet British demands may be realised when it is
stated that"5 for some years prior to the war the imports of
crude zinc into the United Kingdom averaged about 100,000
tons annually.

The bulk of the imported metal, as shown by the table on
p. 26, came from Germany and Belgium, whilst other countries
also contributed smaller amounts. It will be seen that the
cost of this imported metal amounted to the enormous sum of
£3>5oo,ooo annually, a fact which shows how important an
adequate supply of the metal is to British industries, even under
normal conditions.

In addition, however, to the imports of crude zinc, about
20,000 tons of manufactured zinc, largely sheet metal, and valued
at about £600,000, was imported annually into the United
Kingdom in the few years immediately preceding the war.

It will be seen that in 1913 the zinc imports amounted to as
much as 145,000 tons, whilst the zinc produced in the country
in 1913 totalled only 58,298 tons, representing 5-9 per cent,
of the world's production of zinc for that year, which was

THE RISE AND PROGRESS OF THE PRODUCTION
BRITISH PRODUCTION OF ZINC 1875-1915

20,000

15,000

0.000

1875 '860

THE ZINC INDUSTRY

985,142 tons. It must, however, be pointed out that of the
total metal produced in Great Britain in 1913 probably not more
than 31,290 tons were " primary " zinc in the sense of being
extracted from ores, the balance of 27,008 tons being the result
of treatment of by-products, galvanisers ashes, hard-zinc, etc.1

It will be seen, therefore, that this country in the year before
the outbreak of war was producing — even including "secondary "
metal— only about 26*0 per cent, of its zinc requirements.

For many years the galvanising industry has been by far the
largest consumer of zinc in this country, probably requiring
at the present time nearly 70 per cent, of the total zinc con-
sumed in Great Britain.

With this very important field of zinc consumption so close
at hand, it is difficult to explain why British zinc smelters have
made so little progress and have allowed the output of metal
to fall so far short of the demand that prior to the war fully
two-thirds of the British zinc requirements were imported from
the Continent and to a small extent from America.

There is doubtless some justification for the assertion that,
as the ores of zinc which are to be found within the limits of the
British Isles do not equal in importance those of some of the
foreign zinc producing countries, the home production of the
metal has had to struggle against the superior advantages of
some of the foreign sources of supply. But, as pointed out by
J. Gilbert,2 more than one half of the zinc imports to the United
Kingdom have hitherto come from Belgium and the Rhine dis-
trict, where for some years fully 33 per cent, of the European
production of zinc has been produced almost exclusively from ore
imported from all parts of the world ; consequently the above
assertion loses much of its weight. One must therefore look for
other causes in order to explain the apparent neglect of the
zinc industry in Great Britain, and the principal one will be found
in the fact that the British smelters have scarcely availed them-
selves to any great extent of the enormous progress made by
the Continental smelters in the improvement of their furnaces,
whereby they have been enabled to reduce the former considerable
loss in smelting by from 33 to 50 per cent. This source of economy
became of special importance when the old supplies of the rich
and comparatively easily smelted carbonate of zinc (calamine)

1 Rudolf Wolff & Co., published statistics for 1913.
? The Mining Journal, 1916, vol. cxiv, p. 480.
22

THE RISE AND PROGRESS OF THE PRODUCTION

were gradually diminishing, and the treatment of the originally
neglected sulphide of zinc (blende) had to be resorted to.

The experiments in that direction, started in Germany and
Belgium some twenty years ago, have gradually led to such
important improvements in the old type of furnaces, chiefly in
reducing the ruinous loss in smelting and in the saving of
fuel, retorts, and labour, that these factors may be considered
as the principal sources of prosperity of the Continental " Lohn-
huetten " (" customs ") works, that purchase ores for treat-
ment, in contradistinction to " Grubenhuetten " works, which
treat ores produced by their own mines. Most of the " Lohn-
huetten " companies, during the last ten to twenty years, have
equipped their works with modern furnaces.

As J. Gilbert remarks, " Unfortunately, the British zinc
smelters and consumers have not watched the rapid development
of the industry on the Continent, which went hand in hand with
some enormous contracts for ore, chiefly from mines situated in
the British Colonies, with sufficient alertness to enable them to
participate in the financial results realised during the last decades,
to such an extent as their position as principal consumers of
zinc in Europe might entitle them.

" The smaller British zinc companies shrank from the responsi-
bility which the outlay for the comparatively expensive modern
plant would involve, and the larger companies most likely had
sufficiently profitable employment for their capital and labour
in other metallurgical enterprises, that the prospects of zinc
might have appeared to them as a quantite negligeable. Thus,
generally speaking, very little progress has been made by British
zinc makers during the last thirty to forty years, which fact is
also shown by a comparison of the values of British zinc shares
with, for instance, Belgian shares."

Although economic reasons have had something to do with the
lack of enterprise in the British zinc industry, it would appear
that a certain amount of conservatism, and perhaps an undue
regard for local tradition on the part of the zinc metallurgists
and the natural desire of our financiers to see a fair return on
their capital, such as they have hitherto more readily obtained
elsewhere, are mainly responsible.

Two important circumstances which also appear to have
retarded the development of the British zinc smelting industry
are lack of scientific control and want of co-operation between

THE ZINC INDUSTRY

the different smelting companies, in which respects the British
industry compares unfavourably with that of the Continent.

The increasing cost of production during the past few years
has emphasised the necessity for scientific control.

Whilst there are instances where individual firms keep them-
selves informed regarding scientific developments in zinc metal-
lurgy and make efforts to improve working methods, there is
little doubt that a fuller appreciation of the value of the scien-
tifically trained metallurgist and of co-operative action is
needed in order to produce general increased efficiency. This
statement should not, however, lead to the erroneous conclusion
which some persons are inclined to draw, that British metallurgists
are too ignorant of chemical knowledge to understand the theory
of the processes under their direction. It is not too much to
affirm that with respect to knowledge, both of the theory and
practice of the special departments of the art in which they
are engaged, the zinc smelters of this country are in many
cases not excelled by any metallurgists in Europe. But while
progress, although slow, has been made in the past, much more
will have to be done in the future, since the unprecedented times
through which we are now passing demand a long step forward
in knowledge, equipment, and organisation. The advantages
of co-operation are too self-evident to need emphasising here.

As has been well said,1 " the spirit of co-operation is not a
mere sentiment or theory. It has been as much a scientific
necessity for the winning of this war as the provision of guns
and ammunition, and it will be equally a scientific necessity to
success in the arts of peace." Co-operation will be secured as
the result of confidence between individual firms engaged in the
same industry and between employer and employed. The
value of co-operation has long been recognised by the zinc smel-
ters on the Continent. Some years ago a society was started in
Germany in the interests of the producers of non-ferrous metals,
and sections were formed to deal with special branches of industry,
including a zinc section consisting of the managers and higher
technical officials of the zinc smelting works.2 They met at the
same time as the half-yearly meetings of the society, and

1 Prof. W. Ripper, " Works Organisation and Efficiency," Journal of
Royal Society of Arts, 1917, vol. Ixv, p. 461.

2 H. M. Ridge, Journal of the Society of Chemical Industry, 1915,
vol. xxxiv, p. 764.

THE RISE AND PROGRESS OF THE PRODUCTION

exchanged experiences confidentially. No reports of the sectional
meetings were published, since they were only for the mutual
benefit of the members and for the promotion of German
industry, but the system has given excellent results. Some
such system might with advantage be adopted in this country.
The first step would be to consider the means needed to
overcome the hindrances which have occasioned the lack of
co-operation in the past.

Probably an amalgamation of various zinc smelting works
would be the easiest means of attaining the desired end.

It is necessary to realise that the industry must move forward
as a whole if the greatest advantage is to be gained, and this
can only occur by the loyal co-operation of those engaged in
it and by the cultivation of a spirit of confidence in each
other.

It is much to be regretted that the schemes so far suggested
will not increase the British output of zinc sufficiently to
relieve entirely consumers of their dependence on foreign
supplies.

The proposals that have been made for the development of
the zinc industry are dealt with in Chapter XIII (p. 198).

Speaking generally, it may be said that the British zinc in-
dustry has always been dependent on imported ores. Almost
as soon as the industry became firmly established important
zinc mines in Sardinia were operated by British zinc smelting
companies, the ore being shipped to Swansea for treatment. As
early even as 1870 the small production of zinc ore in Great
Britain was decreasing, the output for that year amounting to
only 18,500 tons, equivalent to approximately 5,000 tons of
metallic zinc, whilst a considerable tonnage of zinc ore was
exported from Sardinia to Swansea in that year. From that
time forward the British smelters have imported increasing
quantities of zinc ore annually.

For many years the zinc mines in the United Kingdom have
yielded only an average output of some 17,000 tons, the bulk of
which was mined by the Vieille Montagne Zinc Company of
Belgium, and exported to that country for treatment. The
small quantity of British ores smelted in this country produce
about 2,500 tons of zinc annually, the remainder of the metal
produced in the United Kingdom being obtained from imported
ores as already stated.

THE ZINC INDUSTRY

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THE RISE AND PROGRESS OF THE PRODUCTION

The quantity and the sources of zinc ore imported into the
United Kingdom for the three years 1912 to 1914 are shown in
the table on p. 26.

There are almost unlimited supplies of high grade zinc ore
within the British Empire that have long been available for
zinc smelters, but it is only within quite recent years that any
quantity of the ore has found its way to this country for the
extraction of the metal.

It will be seen from the table on p. 26 that in 1914 there was
a very large increase in the quantity of ore imported from Australia.
Prior to the war a very considerable proportion of the Australian
output of zinc ore was controlled by German firms and shipped
to the Continent for smelting. Further reference to this question
will be found on p. 152.

It is very regrettable that so much of the work done by
Englishmen in devising means of dressing the vast supplies of
zinc-lead ores of Broken Hill, Australia, should have merely
resulted in our becoming suppliers to the Continental smelter
firms who readily treated such ores, because our smelters were
not prepared to pay a price which would induce the sellers to
send them to this country, or to adapt their furnaces for their
special treatment.

There are now seventeen works producing zinc and remelting
scrap zinc, etc., in Great Britain, seven being situated in the
Swansea Valley, the chief centre of production, and the remainder
in different parts of the country.

In the selection of a locality for the erection of zinc works,
it is requisite not only that the ore should be delivered
at a reasonable price, but also that good coal and very
superior fireclay should be readily obtainable. These con-
ditions are well met in Swansea, and on that account
this district was early selected as the chief seat of the British
industry.

About ten works produce zinc direct from ores to the extent
of approximately 31,000 tons, while the remaining seven works
produce " secondary " zinc amounting to approximately
27,000 tons, thus making the total output 58,000 tons for 1913.
The bulk of the secondary zinc is extracted from the by-products
of the galvanising works, and the zinc works for the treatment of
this material are therefore usually situated near the centres
of the galvanising industry.

THE ZINC INDUSTRY

The actual position of the works producing zinc in the
United Kingdom is shown in the following list :—

LIST OF ZINC SMELTERS AND ZINC EXTRACTORS IN THE UNITED KINGDOM.

County.
Cheshire . .

Durham . .
Glamorganshire .

Lancashire

Middlesex
Somersetshire

Warwickshire
Worcestershire

Ayrshire . .

Owner of Works.

Brunner, Mond & Co.,
Ltd.

Central Zinc Co., Ltd.

British Metals Extrac-
tion Co., Ltd. (Villiers
Smelting Works).

Dillwyn & Co., Ltd.

Down & Co., Ltd.

English Crown Spelter
Co., Ltd.

Williams, Foster & Co.,
and Pascoe, Grenfell
& Sons, Ltd. (Upper
Bank Spelter Works)

Swansea Vale Spelter
Co., Ltd.

Vivian & Sons (Morris-
ton Spelter Works).

New Delaville Spelter
Co., Ltd.

The British Electro-
lytic Zinc Co.

Thos. W. Ward, Ltd.

John Lysaght, Ltd.
New Delaville Spelter

Co., Ltd.
New Delaville Spelter

Co., Ltd.
Stewarts & Lloyds,

Ltd. (Coombs Wood

Tube Works).
Brands Pure Spelter

Co., Ltd.

Situation of Works.
North wich.

Seaton Carew.
Llansamlet.

Llansamlet.

Swansea.

Swansea (Port Ten-

nant).
Swansea.

Llansamlet.
Swansea.
Warrington.
Widnes.

Silvertown,

London, E.
Bristol.
Bloxwich.

Birmingham.

Halesowen, near Bir-
mingham.

Irvine (Glasgow).

Previous to the war the Swansea Vale works belonged to an
influential German firm, who had installed a modern smelting
plant capable of producing 10,000 tons of spelter per annum.
Practically all the shares in the company are now held by the
Share Guarantee Trust, Limited, and the works, which are now
the largest in Swansea, are being further enlarged.

The works at Seaton Carew, Durham, which are modern and
well equipped, are operated by the Sulphide Corporation, and
before the outbreak of war were treating annually some 10,000

THE RISE AND PROGRESS OF THE PRODUCTION

to 12,000 tons of zinc concentrates from the Broken Hill mines ;
since the war the works have been enlarged, and a considerable
increase in output of zinc from these ores will result in future.

Formerly the whole of the zinc produced in Great Britain
was extracted by distillation, but within recent years the deposi-
tion of zinc from solution by electrolysis has been introduced
by Messrs. Brunner, Mond & Co., Ltd., Northwich, and zinc of
very high grade is now being produced by this method. Since
the beginning of the war Messrs. Chance and Hunt, of Oldbury,
and the British Electrolytic Zinc Company, of Widnes, have also
commenced the production of electrolytic zinc, for which there
is an increasing demand on account of its freedom from impurities.

British Empire Centres of Zinc Production

In addition to the old-established zinc smelting centre of
Swansea, various plants have been erected in modern times
to deal more particularly with zinc ores occurring within the
British Empire.

Many of these ores are of a complex nature, and in connection
with their treatment there has been a very important
development in the field of electrolytic methods of zinc extrac-
tion.

Australia. — Foremost amongst the newer smelting plants are
those erected at Port Pirie and at Cockle Creek, near Newcastle,
New South Wales, to smelt the lead ore product from the vast
deposits of complex lead-zinc sulphides mined at Broken Hill.
The nature of these ores is dealt with later (see p. 53).

The satisfactory treatment of these ores for the recovery of
both lead and zinc has presented considerable difficulties to the
metallurgist, and it is only within quite recent years that the
profitable extraction of zinc has been rendered possible. The
modern methods of dressing the ore yield two products, one of
which is rich in lead and is smelted for that metal, and the other
rich in zinc, which is smelted for its zinc content.

(The Port Pirie smeltery takes the lead concentrate and the
zinc concentrate from the Broken Hill Proprietary, Zinc Corpora-
tion, Junction, Junction North and Amalgamated Zinc Companies.
The Sulphide Corporation smelts its lead ore at Cockle Creek,
together with the lead ore from Block 14 Mine. In the earlier
working of the Broken Hill deposits for lead and silver, the zinc

THE ZINC INDUSTRY

was neglected and enormous quantities of zinciferous tailings
and slimes accumulated from the concentrating plants.

In addition to these, some of the slags from the lead smelting
contained from 16 to 20 per cent, of zinc oxide. It was
estimated by the New South Wales Department of Mines that
in 1903 there had accumulated zinc residues and tailings amount-
ing to 5,687,400 tons, and these contained 18-6 per cent, of zinc.
Numerous processes were tried in order to produce a marketable
grade of ore from these residues, and it was finally decided that
flotation processes were the most suitable.

The importance of these residues at the present time is well
illustrated by reference to the operations of only one company,
the Amalgamated Zinc Company, which in 1913 treated 498,289
tons of tailings which contained zinc, 17-1 per cent. ; lead, 37
per cent., and silver, 4-4 oz. per ton.1

From these residues there were obtained 140,098 tons of zinc
concentrates carrying zinc, 48-9 per cent. ; lead, 5-9 per cent.,
and silver, 8-5 oz. per ton. The lead concentrates also produced
amounted to 1,584 tons and contained lead, 57-1 per cent. ;
zinc, 15 per cent., and silver 35-2 oz. per ton. The lead and
zinc concentrates together were valued at £392,182. In 1913,
the total value of the products obtained by the companies
engaged in treating zinc-bearing tailings was £776,228.
Most of the " dumps/' or reserves of tailings, have now been
treated.

The annual output of crude ore from the Broken Hill district
amounts to about 1,700,000 tons, and employment is found for
about 8,800 men. These figures give some idea of the great
importance of the deposits as a potential source of lead, zinc
and silver.

The annual output of zinc concentrate in normal times is
approximately 500,000 tons, valued at about £1,500,000. Prior
to the war, about 41-5 per cent, of the lead concentrates produced
at Broken Hill was smelted at Port Pirie, and 8-5 per cent, at
Cockle Creek, while the remaining 50 per cent, was dispatched
to Belgium, Germany, France and Austria, where it was handled
almost entirely by German firms. Of the zinc concentrates,
only about 2-5 per cent, was smelted annually at Port Pirie,
and with the exception of some 20,000 tons which is exported

1 Bulletin of the Imperial Institute, 1915, vol. xiii, p. 621.

THE RISE AND PROGRESS OF THE PRODUCTION

to the United Kingdom and smelted at the works of the
Sulphide Corporation at Seaton Carew and other works, the
bulk of the remainder was dispatched to smelters in Belgium
and Germany under long term contracts.

The disposal of the lead concentrates was on very different
lines, at least onejialf of the ore being smelted locally, as stated
above, and the remainder sold under short-date contracts,
chiefly to German firms.

The output of zinc from the Australian smelting plant has,
up to the present, been too small to have any effect on the world's
production, owing to the large amount of zinc concentrate
shipped before the war to Europe, but which, in view of the
proposal to enlarge the Port Pirie smelting plant, may become more
important in the near future. This extension forms part of the
scheme that has been proposed since the outbreak of war with
a view to increase the output of zinc within the British Empire.

Tasmania. — Some experimental plants are in course of erection
in Tasmania for the treatment of the complex zinc-bearing ores
of the Mount Read district by electrolytic methods. Reference
to the processes to be used will be found on p. 134.

This enterprise, which has been discussed for some ten years,
embraces, not only a large plant which is being erected by the
Australian Electrolytic Zinc Company, with a suggested capacity
of 45,000 tons of zinc per annum, and Gillie's works at Hobart,
but all the fresh range of output from the Tasmanian West
Coast ores.

Canada. — Although zinc ores have been mined in Canada for
some years, it is only quite recently that attempts have been
made to treat them in the country. Formerly the ore was
shipped to the United States for treatment, but since the outbreak
of war considerable attention has been given to the question of
treating the ore in Canada.

To encourage the erection of zinc extraction plants, the
Canadian Government recently agreed to grant bounties on a
sliding scale, not exceeding 2 cents (i^.) perlb., on the production
of zinc in Canada from Canadian ores when the standard price
of zinc in London (England) falls below £33 per ton of 2,000 Ib.
Such zinc must not contain more than 2 per cent, of impurities.

There are deposits of low grade and leady zinc ores in Canada
that can only with difficulty be concentrated so as to produce
high grade lead and zinc concentrate respectively.

THE ZINC INDUSTRY

In the past there has been a moderate production of zinc
concentrates for export to American smelters, the treatment
charges and high freight rates serving to prevent any very
extensive development in this direction. Some 7,000 to 9,000
tons of zinc ores and concentrates, containing about 3,000 to
4,000 tons of zinc, have been shipped annually in recent years.
At the beginning of the war the smelters in the United States
declined to take further shipments of zinc ores from British
Columbia, and there was at that time in Canada a shortage of
zinc for use in manufacturing ammunition and a quantity of
zinc ore that could not be disposed of. A Commission was
appointed by the Minister of Militia and Defence to look into
the matter on behalf of the Government.1 It was found to be
impossible to obtain the pure zinc for use in the manufacture of
cartridge brass from the British Columbia ores by an}' distillation
process, whether in the Belgian retort or in the electric furnace.
It was therefore necessary to turn to hydro-metallurgy, and after
a large amount of experimental work a process has been developed
at the works of the Consolidated Mining and Smelting Company
at Trail, B.C., and at some other smelters, which is a modification
of the well-known Letrange process, the ore being roasted,
leached with sulphuric acid, and the resulting zinc sulphate
solution electrolysed with insoluble anodes. During 1916 a
large plant was built at Trail, costing perhaps 1,000,000 dollars,
and capable of producing 30 or 40 tons of electrolytic zinc per
day, which should meet in large measure the present requirements
for cartridge brass in Canada.

Similar work is going on at Welland in Ontario, at a large
plant owned by the Weedon Mining Company. Prof. Stansfield,
of McGill University, considers that " this development was
undoubtedly the best under the existing circumstances, but it
must not be supposed that it disposes of the possibility of smelting
these ores in the electric furnace." The works at Welland will
be supplied with ore from the mines owned by the company
at Welland and at Nottingham, Quebec.

According to a recently issued report of the Canadian Depart-
ment of Mines, Ottawa, the shipments of zinc ores to America
in 1915 amounted to 14,895 tons, valued at 554,938 dollars,
and containing 12,231,439 lb. of zinc.

1 A. Stansfield, Journal of the Institute of Metals, 1916, No. i, vol. xv,
p. 292.

THE RISE AND PROGRESS OF THE PRODUCTION

Assuming a probable recovery of 80 per cent, of the metal,
the production of zinc in 1915 from Canadian ores may be put
at 9,785,151 Ib. (approximately 5,000 short tons), valued at
1,294,575 dollars. Adding to the result of a similar estimate for
1916 the actual output of zinc at Trail, it would appear that the
production of zinc from Canadian ores in that year was 23,515,030
Ib. (approximately 12,000 short tons), valued at 3,010,864 dollars.
According to the Report for 1916 of the British Columbian
Minister of Mines, the output of zinc from the smelter at Trail in
that year was approximately 15,000,000 Ib. (7,500 short tons).
At the beginning of 1917 the output of the smelter was stated
to be from 25 to 30 tons per day.

The Development of the European Zinc Industry

The position taken by Europe as the largest contributor to
the world's supply of zinc has been maintained until the present
time. In 1913 Europe's share of the world's output of zinc was
673,900 metric tons, or 67-5 per cent, of the world's total output
for that year.

The bulk of the metal was produced in Germany and Belgium.
Thus, in 1913, Germany's output was nearly 42 per cent, of
Europe's production and about 28-4 per cent, of the world's
total for that year, whilst Belgium contributed about 40 per
cent, of the European production.

The zinc production of the remaining European countries is
much smaller than that of Germany and Belgium.

The British output hardly exceeds 10 to 12 per cent, of the
European production, whilst British consumers of zinc absorb
about 40 per cent, of the European output.

Next in importance as producers in Europe are France,
Holland, Austria-Hungary, Norway and Sweden.

Compared with the old-established British, German and
Belgian industries, zinc production in the other European
countries must be regarded as of comparatively modern origin.

As the result of the ever-increasing demand for zinc, the
European zinc industry made rapid progress, notably in Ger-
many and Belgium, during the latter part of the nineteenth
century.

Germany. — Taking advantage of her extensive natural resources
in zinc ore and coal, Germany early took the lead as the largest

33 D

THE ZINC INDUSTRY

producer not only in Europe, but in the world, a lead which she
maintained for many years ; but in recent years the first place
in the world's zinc producers has been taken by America.

The growth of the zinc industry in the German Empire is
shown by the following figures : — In 1862 the output was about
55,000 metric tons ; in 1872 it amounted to 58,400 tons ; ten years
later the output had nearly doubled, the total for 1882 being
about 106,000 tons, while in 1892 it had reached a total of
approximately 140,000 tons, thus showing an increase of about
139 per cent, in twenty years, equivalent to an advance of about
8 per cent, per annum since 1885.

A further ten years saw a considerable augmentation of output,
the total for 1902 being about 190,000 tons, which had increased
to approximately 271,000 tons in 1912.

The production for 1913 was 283,113 tons, showing an enor-
mous increase on the output of ten years previously.

The chief zinc producing centre of Germany is Silesia, the
output from this district being about two-thirds of the total
production of the German Empire, the remainder coming chiefly
from the Rhine district and Westphalia.

The actual production of zinc, in metric tons, from these two
districts in recent years is shown in the following table l : —

PRODUCTION OF GERMAN ZINC IN METRIC TONS (2,204-6 LB.)

District.

1909.

1910.

1911.

1912.

1913-

Silesia
Rhine District and
Westphalia

139,690
75,173

140,249
78,765

156,174
81,458

169,088
86,619

170,119
92,852

The Silesian zinc industry is confined to the extreme south-
eastern part of Prussia, in a somewhat narrow strip of territory
between Russia and the Austrian frontier.

Established, as already stated, in the latter part of the
eighteenth century, it was prior to the war an industry of
considerable magnitude, taking a very prominent part in supply-
ing the European markets with zinc.

Formerly the metal was produced entirely from domestic

1 Compiled by Henry R. Merton & Co., London.

THE RISE AND PROGRESS OF THE PRODUCTION

ores, but in more recent years considerable amounts of ore have
been imported.

For some years Germany has adopted the policy of conserving
national resources for the future, and of buying ore in foreign
markets when this could be done on terms which would permit
of a good profit on the smelting.

It has been stated recently1 that several of the mines in
Silesia, particularly those of Hohenlohe and Giesche, have
milling and concentrating plants which are only being worked
to something between 30 and 40 per cent, of their possible
capacity. The Von Giesches Erben is reported to possess ore
reserves which at the rate of mining in 1914 are estimated to
last for more than 100 years.

From the reports which have reached this country since the
war commenced, it would appear that Germany has suffered no
shortage of zinc, her domestic ores and established smelting in-
dustries having supplied all demands and enabled the metal
to be sold at very little above the pre-war average price.

The zinc smelting industry of Upper Silesia is in the hands
of several large firms, the metallurgists of which stand at the
head of their profession and have brought the industry to a
high state of perfection.

The works are divided into two main classes — (i) the " Gruben-
huetten " or " Erzhuetten " companies, which smelt ore produced
by their own mines, and (2) the " Lohnhuetten " companies,
which buy ore in the market.

These latter have yielded good profits in recent years, being
supported by the leading wealthy metal and mineral trading
companies, who have large interests in the zinc industry.
Nothing has been spared to develop the dominant position
taken by the German zinc industry, and during the past ten years
most of the works have been reconstructed and supplied with
modern gas-fired furnaces, and many improvements have been
introduced into botn the roasting and smelting processes.

Although the number of smelting concerns engaged in the
zinc industry in 1870 was 35, the number had been reduced to
29 in 1890, but the capacity of these works was increased so that
the output of metal was augmented. Since 1890, a few new
works have been added to enable the output to be brought to
the large figure which represents the modern production.

1 H. M. Ridge, Journal of the Institute of Metals, 1916, vol. xvi, p. 187.

35 D2

THE ZINC INDUSTRY

The German output of zinc, in metric tons, for the ten years
ending 1913 is as follows : —

GERMAN OUTPUT OF ZINC.

Year.

Metric tons.

Year.

Metric tons.

1904

191,060

1909

220,080

1905

197,184

1910

227,747

1906

205,023

1911

250,393

1907

208,707

1912

271,064

1908

216,876

1913

283,113

Since the production has for many years been in excess of
the consumption of zinc in Germany, the surplus metal has
been exported, chiefly to the United Kingdom.

The smelting of sulphide zinc ores in Germany led to the
establishment of very complete arrangements for utilising the
sulphurous acid generated in the roasting of the ore, the first
practical results in this direction being obtained by Hasenclever
as early as 1855.

Most of the works are now equipped with special roasting
furnaces, which permit of the roast gases being used for the
manufacture of sulphuric acid, and there is little doubt that the
utilisation of the sulphur in zinc ores for this purpose has con-
tributed very materially to the success of the Continental zinc
smelting industry.

Sulphuric acid is a by-product of considerable commercial
value, and consequently a source of additional profit to zinc
production. The question of roasting blende for sulphuric acid
production is more fully discussed when dealing with the by-
products from zinc smelting on p. in.

In addition to the production of zinc and sulphuric acid, the
Silesian industry includes a number of zinc-rolling mills which
contribute a considerable quantity of sheet metal to the world's
requirements. Prior to the war, eight mills were producing about
50,000 tons of sheet metal per annum.

Austria- Hungary. — The zinc production from these countries is
comparatively small, although the output has gradually increased
in recent years. The output rose from 19,600 metric tons in
1912 to 21,700 tons in 1913. The larger proportion of the metal

THE RISE AND PROGRESS OF THE PRODUCTION

is produced at the works in Galicia, whilst rather less than 50
per cent, is obtained at the works at Steiermark.

Belgium. — As already stated, Belgium early became the second
largest zinc producer in Europe, producing about two-thirds
of the European output in 1890, but so rapid has been the
increase in later years that prior to the war the output almost
equalled that of Germany.

The Belgian zinc production in recent years is shown in metric
tons in the following table : —

BELGIAN OUTPUT OF ZINC.

Year.

Metric tons.

Year.

Metric tons.

1904

139,982

1909

167,100

1905

145.592

1910

172.578

1906

152,461

1911

195,092

1907

154.492

1912

200,198

1908

165,019

1913

I97.703

Zinc rolling also forms an important branch of the industry,
the production of sheet metal in 1913 being 51,500 metric tons,
as against 49,100 tons in 1912.

A small proportion of the output of crude zinc is utilised
for the production of zinc oxide (zinc white) by burning the
metal in air as described later (p. 192).

The Belgian industry was founded to utilise the important
deposits of ore in the country, but since 1856 the yield of native
zinc ore has been comparatively small, so that it has been neces-
sary to import increasing quantities of foreign ores to maintain
the large production of metal in modern times. Within recent years
considerable quantities of zinc concentrates from Broken Hill,
Australia, have been smelted in the country. The Belgian zinc
smelting works are situated in the neighbourhood of Liege and
are owned by the well-known Vieille Montagne Spelter Company ,
but are largely under German control.

The company has works, or mines, not only in Belgium, but
also in France, Germany, Sweden, England, Algeria and Italy.

Much that has been said regarding the German zinc smelting
works applies equally to those in Belgium.

The works are well equipped with modern plant, including
gas-fired furnaces and roasting furnaces which permit of the

THE ZINC INDUSTRY

utilisation of the sulphur gases for the production of sulphuric
acid. Prior to the war there was a considerable surplus in the
production of this commodity in Belgium in consequence of the
enormous quantities of zinc blende roasted in that country.

The future of the Belgian zinc industry is very uncertain,
as there is some doubt as to the fate of the works when the
enemy are obliged to evacuate the country.

It is reported that the Germans are keeping together the
skilled labour of the Belgian zinc works, and that they are
assisting in the running of some of the works, but since the
available supplies of ore are limited it is doubtful whether the
yield can be very large.

The German control of the Belgian zinc industry is not likely
to continue after the war.

France. — The production of zinc in France is very little in
excess of that required for home consumption. Although a
moderate producer of zinc ore, much of the ore smelted is of
foreign origin. The smelting works are situated at Pontgiband,
and in recent years the metal produced has been of high grade.
In 1912 France contributed 64,300 metric tons of zinc to Europe's
supply, and 61,100 tons in 1913, thus showing a small decrease.
In each of these years about 5,000 tons were exported to the
United Kingdom.

The consumption of zinc in France amounted to 82,000 tons
in 1912, and 81,000 tons in 1913, thus showing a falling off.

Holland. — Zinc production in Holland has shown a steady
increase in recent years, the production for the ten years ending
1913 being as follows : —

PRODUCTION OF ZINC IN HOLLAND.

Year.

Metric tons.

Year.

Metric tons.

1904

I3.099

1909

i9,548

1905

13.767

1910

20,975

1906

14.650

1911

22,733

1907

14,990

1912

23,932

1908 I7»257

1913

24.323

Spain. — Only a small proportion of the zinc ore raised in
Spain is smelted in the country, the bulk being treated in France
and other centres of production.

THE RISE AND PROGRESS OF THE PRODUCTION

The leading Spanish zinc works are those of Penarroyain
Cordoba and Arnao in Oviedo. The output amounted to 8,000
metric tons in 1912 and 10,000 tons in 1913. In April, 1915,
the export of zinc in cakes was embargoed, and on January I,
1916, an export tax equal to 375. 6d. was placed on zinc in pigs,
blocks and waste articles, and the import duty was removed.

Norway. — Within recent years Norway has become a small
producer of zinc, the output in 1911 being 6,680 metric tons,
that of 1912, 8,128 tons, and 9,287 tons in 1913.

Sweden. — A special feature of zinc production in Sweden is
the application of electric smelting processes to which reference
is made later (p. 124). The development of these processes
has been rendered possible by the plentiful supply of water
power in the country, which has been utilised for generating the
necessary electrical power.

Sweden produced, in 1913, 6,900 tons of ordinary zinc and
2,000 tons of fine zinc.

Russia. — Up to the present the production of zinc in Russia has
been small, the zinc smelting industry being of comparatively
recent introduction. There are good deposits of zinc ore in the
country, more especially in Poland, the chief sources of the ore
smelted being the mines at Ulisses and Boleslaw, near Olkusch.
Prior to the war the annual output of zinc in Russia was
between 8,000 and 9,000 metric tons, whilst the average con-
sumption was more than three times this amount.

The production, in metric tons, for the ten years ending
1913 was as follows *• : —

PRODUCTION OF ZINC IN RUSSIA.

Year. Metric tons.

Year.

Metric tons.

1904

10,606

1909

7,945

1905

7,642

1910

8,631

1906

9,610

1911

9,936

1907

9,738

1912

8,763

1908

8,839

1913

7,610

Owing to heavy requirements in roofing sheets, Russia con-
sumed 33,300 tons of zinc in 1913, as compared with approxi-
mately 28,000 tons in 1912. On the other hand Russia's
1 Compiled by Henry R. Merton & Co.

THE ZINC INDUSTRY

production declined in 1913 to the extent of 1,200 tons, as
shown, which was made up for by the increase of 6,600 tons in
her imports of zinc in cakes and sheet metal. To meet home
requirements Russia has hitherto been obliged to import over
20,000 tons of zinc annually, most of which was obtained from
Germany.

It would appear that attempts are now being made to develop
the Russian zinc smelting, as, according to the United States of
America Consular Report for 1916, a large zinc smelting works
is being erected at Hikoshuna, in the Shimonoseki Straits, by
the Su uki Shoten of Kobe. It is proposed to treat at these
works ore derived chiefly from Asiatic Russia and Australia.

The Development of the American Zinc Industry

Although started more than half a century later than that
of Europe, the American zinc industry has made such rapid
progress, especially during the past few decades, that the United
States have since 1906 held the premier position as a producer
of zinc.

In 1913 the United States contributed 32*1 per cent, of the
world's supply of zinc, whereas Germany, formerly the largest
producer, contributed 28*4 per cent.

This rapid growth of zinc production in the United States
has been rendered possible by the possession of very large
quantities of raw material in the form of zinc ore. and of coal,
and more particularly of large supplies of natural gas, which,
in some localities, is used as the source of heat in smelting the
ore, and has proved to be of considerable importance in the
economic production of the metal.

The remarkable progress of the American zinc industry
affords a striking illustration of the speed with which industrial
enterprises develop under the combined influence of great
natural resources and of modern smelting plant used with in-
telligence and skill.

This progress can best be seen by comparing the data of
production thirty years ago with those of the present time.

In 1885 the total production of zinc in the United States
amounted to only 40,000 metric tons, whilst the production
in 1905, twenty years later, had increased five-fold, being more
than 200,000 tons. By 1913 the output had increased more

THE RISE AND PROGRESS OF THE PRODUCTION

than 50 per cent., and since the outbreak of war the production
of zinc in America has reached nearly twice the pre-war figure,
as shown by the following returns : —

ZINC PRODUCTION IN THE UNITED STATES IN METRIC TONS.

Year.

Metric tons.

Year.

Metric tons.

1907
1908
1909
1910
1911

226,838
189,941
240,446
250,627
267.472

1912
1913
1914
1915
1916

314.512
320,283
328,731
446,788
609,906

With the growth of the industry, zinc smelting works were
established in the States of Illinois, Kansas and Missouri, which
in pre-war days produced about two-thirds of the total output
of American zinc, the remainder being produced in a few Eastern
and Southern States.

In consequence of a falling-off in the yield of the natural
gas springs of Kansas and Oklahoma in recent years, it became
necessary to transfer the works to Illinois and other places where
coal or oil could be obtained in sufficient quantity and at a cheap
rate. At the end of 1914 there were 33 zinc smelting plants in
operation in the United States, their disposition being as follows :
Illinois 10, Kansas 9, Oklahoma 6, and the remaining 8 in the
States of West Virginia, Missouri, Pennsylvania and Colorado.

The works are independent of each other, so that the com-
petition for ore is keen.

The American zinc industry has always been independent of
the European industry, and it is generally agreed that in normal
times America is not favourably situated to compete with the
European markets, and the shipment of zinc to the United
Kingdom only becomes possible when the zinc market is abnor-
mally high, as it has been since the outbreak of war. American
smelters have the advantage of being entirely independent of
foreign ore, as they have enormous native deposits on which to
draw.

The supplies of rich ores from the older districts, such as the
famous Joplin district, on which the smelters formerly depended,
have been considerably augmented in recent years by con-
centrates from the complex ores from the Western States. The

THE ZINC INDUSTRY

greatest impetus was given to the production and utilisation
of the Western ores by the development of the methods for
dressing and separating the complex zinc ores by the aid of
electricity, to which reference is made on p. 70.

Previous to the war, the production of zinc in the United States
was about equal to the consumption in that country ; thus in
1913 they produced 320,283 metric tons of zinc, and consumed
313,300 tons. The balance available for export was therefore
only 6,983 tons.

The cutting off of the European supplies of zinc at the outbreak
of war resulted in the Allies with one accord turning to the
United States, the largest producer of zinc in the world, for
supplies, and the response made by the American smelters
considerably eased the serious situation in which this country
and her Allies found themselves owing to shortage of zinc for
munition purposes.

The limited supply of zinc available for export, however, led
to a rapid rise in the price of the metal, and the American zinc
smelters have been very highly paid for their services.

The deficiency in the world's supply of zinc has been met by
the rapid erection of additional works in the United States,
and an increase of production has resulted which as the figures
given below show, is unprecedented in the history of the zinc
industry.

As Professor Carpenter remarks, " What these figures mean
can be adequately appreciated only by those who know what
is involved in the expansion of an industry where mining and
ore-dressing operations, transport and assemblage of materials,
erection and operation of furnaces, and, most difficult of all,
the training of the necessary labour are concerned."

Taking the individual States in the order of their zinc output,
Illinois comes first, then Oklahoma, and Kansas third. As
shown by the following figures, these three States are now
producing collectively nearly three-fourths of the total output

of zinc in the United States.

1915. 1916.

State. Metric tons. Metric tons.

Illinois ,1. .. .. 145,105 163,612

Oklahoma ..' .. .. 99,073 148,859

Kansas . . . . . . 92,010 127,475

Other States .. .. .. 107,892 157,429

Total ,v - .. .. 444,080 597.375

THE RISE AND PROGRESS OF THE PRODUCTION

Considerable additions are still being made to the smelting
plants, so that the future output of zinc will be greater even
than that for 1916. The full capacity of the furnaces was not
utilised in smelting ore at any time during the past three years ;
a large number of the retorts were occupied in redistilling crude
zinc for the production of high grade metal for munition purposes,
much of which was exported to this country.

In 1916 two new smelteries, with large graphite retorts, were
erected for this purpose. The high prices of zinc ruling during
the past few years have greatly stimulated research in the
treatment of low grade complex zinc ores, and America is now
producing appreciable quantities of high grade zinc from such
ores by electrolytic methods which are described on p. 124.

The enormous increase in zinc production will no doubt make
America a formidable competitor of this country after the war.
The zinc smelters have been making very large profits, and these
have been used wisely in improving the plant, so as to make
it as efficient as possible, and in accumulating great financial
reserves.

In view of the large ore reserves in America, there is no reason
to suppose that there will be any failure to realise the enormous
output expected through smelting plant being in excess of the
capacity of the mines.

Zinc Production in Asia

The Asiatic centres of zinc production, although at present
contributing but little to the world's supply, are by no means
unimportant, especially in view of recent developments in Japan.

China. — As previously stated, China has for several centuries
been a producer of zinc by crude distillation in pots by native
methods, and small quantities of metal made in this manner
have found their way to the European market for very many
years. No details are available as to the amount of metal
produced annually, but the amount of metal exported to Europe
in recent years is stated to be as follows. In 1911, 710 metric
tons ; in 1912, 760 tons, and in 1913, 908 tons. The metal, which
is produced chiefly at Kweichow, probably from carbonate ores,
is of good quality, containing 99-56 per cent, of zinc with a little
lead and iron.

China possesses vast deposits of zinc ores, which in the past

THE ZINC INDUSTRY

have been largely worked by foreign concerns, and the ore exported
for treatment, but the erection of smelting works for the treat-
ment of the ore in the country has been proposed, and possibly
in the future a zinc smelting industry on modern lines will be
established.

Japan. — Zinc smelting in Japan appears to be of recent
origin, although zinc ores have been mined in the country for
many years and exported to European smelting centres for
treatment. The war has, however, given considerable impetus
to the Japanese zinc smelting industry, and plant is being erected
capable of supplying sufficient metal to meet home requirements
and reduce imports of zinc.

The chief smelting works are situated at Osaka and Ohmuta,
the former works producing about twice as much zinc as the
latter.

The Japanese Bureau of Mines reports the quantity of zinc
produced in Japan in recent years as follows : —

PRODUCTION OF ZINC IN JAPAN IN METRIC TONS.

Quality.

1914.

1915-

1916.

Refined zinc

5,966

21,306

39,3^6

Unrefined

zinc

14,138

6,121

2,187

Total .. .;

20,104

27,427

41,503

In 1913 the zinc imported into Japan, in the form of ingots
and sheet metal, amounted to nearly 11,000 tons, whereas in 1914
it was less than 6,000 tons.

The future of the zinc industry in Japan is generally con-
sidered to be exceedingly good, and it is expected that a large
export trade will be carried on after the war. One company
is manufacturing zinc for the export trade. Much of the
Japanese zinc ore contains other metals, such as gold, silver
and copper, and the refining of these metals is carried on in
conjunction with the treatment of the ore. Five new companies,
with a total combined capital of £760,000, have been organised
and operate six works for the treatment of zinc ore produced
in the country.1

1 Report of H.M. Vice-Consul at Tokio. See Journal of the Society
of Chemical Industry, 1917, vol. xxxvi, p. 1119.

THE RISE AND PROGRESS OF THE PRODUCTION

According to the Board of Trade Journal,'1 the supply of ore
for the Japanese zinc smelting works is by no means assured.
The production of zinc ore in Japan does not exceed 50,000
tons per annum, whilst the existing Japanese works need about
three times this quantity if they are to be kept working at their
full capacity. Further, if all the projects for new works and
additional plant are realised, the requirements of the industry
in the near future for zinc ore will exceed 300,000 tons. This
being so, the important question of ensuring a regular supply
of ore is now engaging the attention of the zinc smelters and
the Japanese Government.

During the past two years zinc ore and zinc concentrates
have been imported into Japan from Australia (Broken Hill),
China, Burma, Indo-China and Vladivostok, but no contracts
for future deliveries of zinc ore appear to have been made.

One important Japanese firm secured during 1916 about
11,000 tons of zinc ore from the Schwai-Ko-Schan mine in
China, and recently negotiations have been begun between
these two concerns with a view to contracts for the supply of
large quantities of ore in the future.

Before the war the cost of zinc production in Japan was
nearly 25 per cent, higher than the cost of production in Ger-
many and Belgium, Japan's chief competitors in the zinc
industry, and to this cost must be added the cost of transport
from those countries to Japan. The total Japanese demand
for zinc is estimated at about 29,000 tons yearly, against which
Japanese smelting works have a present productive capacity
of about 45,000 tons per annum. In the near future, when all
the schemes for new undertakings and extensions are completed,
Japanese zinc smelting works will have a productive capacity of
about 100,000 tons, or 70,000 tons in excess of the requirements
of the country. It is stated that schemes are in hand for the
establishment of a galvanising industry on a considerable scale,
which will absorb some of this excess metal.

1 October, 1917.

CHAPTER III

ZINC ORES AND THEIR SOURCES OF SUPPLY

Zinc Ores ; Their Nature, Occurrence and Distribution

ZINC-BEARING minerals are geographically very widely distri-
buted— so widely, indeed, that they are found in almost all metal
mining districts.

The extent of their distribution is well shown in the accom-
panying map of the world, in which the more important zinc ore
producing districts have been marked.

The map was prepared by J. C. Moulden, for his paper before
the Royal Society of Arts, and is reproduced here by his kind
permission.

The ores of zinc are found more particularly associated with
ores of lead, copper and silver, often forming extensive deposits
of considerable complexity which present problems to the
metallurgist, for the practical solution of which a large number
of processes have been devised.

Whilst zinc occurs as a constituent of a very large number
of the ores of other metals, minerals containing the metal in
sufficiently large quantity, and occurring in sufficient abund-
ance to constitute ores of zinc, are comparatively very few.

The metallurgy of zinc necessitates the employment of ores
relatively high in zinc content ; it is, therefore, frequently
necessary to submit the ores to some preliminary process of
concentration to separate the zinc mineral from the other
minerals and gangue, or worthless material, before a product
sufficiently high in zinc content can be obtained for use by the
zinc smelter.

The percentage of zinc in the ore mined is frequently very
low, and often averages not more than 3 per cent., but this is
increased by concentration to 40 per cent, of zinc or more.

ZINC ORES AND THEIR SOURCES OF SUPPLY

THE ZINC INDUSTRY

Of all the minerals containing zinc, three only are of much
importance to the metallurgist ; these are the sulphide (blende) ,
the carbonate and the oxidised compounds usually designated
under the generic term of calamine, and the silicates of zinc.

Two systems of mineralogical classification are in use for
zinc minerals. In this country the carbonate is generally known
as calamine, and the silicate as smithsonite or hemimorphite.
In America the carbonate is known as smithsonite and the
silicate as calamine, whilst the sulphide is commonly called
sphalerite. This double classification frequently leads to con-
fusion, especially amongst students.

The American nomenclature of zinc minerals is, however,
gradually being adopted by British metallurgists.

The principal zinc-bearing minerals and their respective content
of zinc when pure are as follows : —

Mineral.

Composition.

Zinc.

Blende or sphalerite .
Calamine or smithsonite .

Zinc sulphide
Zinc carbonate . ,

Per cent.
67-15

C2-OO

Hydrozincite ....
Willemite

Hydrous basic zinc carbonate .
Zinc silicate

57-10
58-10

Hemimorphite
Zincite

Hydrous zinc silicate ....
Zinc oxide

53'7°
80-25

Franklinite . . ...

Oxide of iron, zinc and manganese .

16 to 21

Zincite and franklinite, the composition of which is variable,
are important as ores of zinc in the United States of America
only and are utilised for the production of zinc oxide.

Although formerly calamine was the most important ore of
zinc, blende is, at the present time, the chief source of the metal.

Zinc blende, sphalerite, termed by miners " Black Jack,"
when pure, contains 67-15 per cent of zinc. It is, however,
usually contaminated with iron pyrites and other metallic
sulphides, and with gangue minerals, so that as received at the
smelting works it usually contains only from 35 to 55 per cent,
of zinc.

Regarding its association with galena (lead sulphide), it maybe
said that most lead mines are also blende producers, and, similarly,
nearly every zinc deposit carries lead. The two minerals are
frequently mined simultaneously, the blende as a subsidiary
source of income to the lead mine.

ZINC ORES AND THEIR SOURCES OF SUPPLY

Dressing operations suffice in many cases to yield the greater
part of the lead as a galena concentrate, suitable for the lead
smelter, and the zinc blende as a concentrate carrying from 45
to 50 per cent, of zinc.

The lead mines of Cardigan and Cumberland in this country
and of Joplin in America, and Broken Hill in New South Wales
are familiar examples.

Lead and silver are sometimes present, in the more complex
ores, in sufficient quantity to permit of profitable extraction from
the residues, after extraction of the zinc.

Germanium has been found to occur in zinc blende from
Missouri and Wisconsin.1 The oxide of zinc prepared from zinc
residues from the zinc distillation furnaces in which these ores
had been treated was found to contain as much as 0-25 per cent,
of GeO2.

Zinc blende is very widely distributed and occurs in large
quantity in Europe, America, and Australia.

Calamine, smithsonite of the Americans, the carbonate of zinc,
is decreasing in importance as an ore of zinc since the deposits in
many localities are more or less exhausted.

The present supplies are largely derived from Upper Silesia,
Austria, Italy, Greece and Algeria.

When pure, calamine contains 52 per cent, of zinc, but it is
usually accompanied by oxide of iron, carbonate of lime, etc.,
which depreciate its commercial value, since these substances
give trouble in smelting if present in appreciable quantities.
Before smelting, calamine is usually calcined to expel the bulk
of the carbon dioxide, thereby decreasing the weight of the ore
and relatively increasing the zinc content.

Hydrozincite is a basic hydrated carbonate of zinc, the only
important deposits of which occur in Spain. Metallurgically
speaking, it differs little from smithsonite.

Willemite is anhydrous silicate of zinc, the best known deposits
of which occur in Franklin, New Jersey, U.S.A., where it is
associated with zincite, franklinite, and calcite, the willemite
forming about 25 per cent, of the deposit. It contains, when
pure, 58-10 per cent, of zinc, but it is usually accompanied by
manganese and other constituents that lower its value materially.

Hemimorphite, electric calamine (calamine of the Americans),

1 " The Occurrence of Germanium in Missouri and Wisconsin Blendes,"
G. H. Buchanan, American Chemical Society, 1917.

49 E

THE ZINC INDUSTRY

a basic hydrated silicate of zinc, occurs associated with the
ordinary calamine or zinc carbonate, with lead ores and with
blende. It is a valuable ore of zinc, although not of such economic
importance as blende or calamine.

It was formerly mined extensively at Aix-la-Chapelle and
Moresnet, in Belgium, but these deposits are now practically
exhausted. Extensive deposits of exceptional purity occur in
Virginia and Missouri, in the United States of America, and
provide the source of one of the purest brands of zinc in the
world obtained by ordinary distillation methods direct.

Zincite, the native oxide of zinc, known as red oxide of zinc,
in a pure condition contains 80*2 per cent, of zinc. It usually
contains oxides of manganese, to which the red colour is con-
sidered to be due, since chemically pure oxide of zinc is white.

Zincite occurs to a limited extent in the extensive ore deposit
at Franklin, New Jersey, forming about 5 per cent, of the
deposit.

Franklinite is a mixture of oxides of iron, zinc and man-
ganese, of variable composition, but containing as a rule from
12 to 18 per cent, of zinc.

It constitutes about 50 per cent, of the deposit at Franklin,
New Jersey. The zinc minerals in this deposit occur as
rounded grains in a crystalline limestone, and are probably the
result of metamorphism. The willemite associated with the
franklinite is separated by a magnetic process and is then treated
for the extraction of the zinc.

The franklinite is treated for the production of zinc white
(commercial zinc oxide), leaving a highly manganiferous residue,
which is smelted in blast furnaces for the production of spiegel-
eisen, a rich manganese-iron alloy used in the manufacture of
steel.

Goslarite, white vitriol, is hydrated zinc sulphate, found chiefly
at Goslar in the Harz, and also sparingly in some of the
Cornish mines and at Holywell, in Flintshire. The mineral
is not, however, sufficiently plentiful to be of much, if of any,
commercial importance.

Zinc minerals in small quantity also frequently accompany
ores of iron and manganese, especially the latter, from which
the zinc, varying from 6 to 10 per cent., is recovered as oxide,
in chambers at the top of the blast furnace, when the ores are
smelted, thus forming a valuable by-product.

ZINC ORES AND THEIR SOURCES OF SUPPLY

The zinciferous flue dust frequently contains as much as
75 per cent, of zinc, and is sold to paintmakers or to zinc
smelters. The production of zinc from such sources is by
no means inconsiderable.

Zinc Ores in the British Empire

Australia is the premier producer of zinc ore within the British
Empire, and in recent years immense quantities have been
obtained from this source.

Ores of zinc are also worked in Canada and in the British Isles,
and deposits of complex ore in Burma and in Rhodesia are already
being actively developed and give promise of becoming a great
national asset and of influencing the world's supply of zinc in a
marked degree in the near future. Zinc ore is found also in
Queensland, Tasmania, New Zealand, Newfoundland, Egypt,
Nigeria, South Africa and, associated with copper ore and
galena, at Tsumeb, in the former German colony of South- West
Africa.

United Kingdom. — The occurrence of zinc ores in the United
Kingdom cannot be considered as extensive, although ores of
zinc, generally associated with lead ores, are found in the
Palaeozoic rocks of Wales, the Isle of Man, the North of England
and the South of Scotland, some of which have been worked
since Roman times.

The best known deposits are those in Flintshire, Cardiganshire,
Durham, Cumberland, Derbyshire, the Isle of Man, Dumfries-
shire and Lanarkshire. The mines are worked for both zinc
and lead, and the ores are subjected to crushing, concentration
and separation to obtain a concentrate suitable for smelting.

Formerly calamine was the chief ore mined in the United
Kingdom, but at the present time the zinc ore is almost entirely
blende, the largest producers being the Nenthead and Nentsbury
Mines at Alston, in Cumberland, and the Carshield Mine in
Northumberland. Prior to the war the output of dressed zinc
ore for the United Kingdom amounted to between 17,000 and
18,000 long tons per annum.

The output in 1913 was 17,294 tons, of which amount England
produced 12,730 tons, Wales 2,601 tons, Scotland (Dumfries)
1,010 tons, and the Isle of Man (Great Laxey Mine) 953 tons.

The Alston mines in Cumberland have for some years been

51 E 2

THE ZINC INDUSTRY

owned and worked by the Vieille Montagne Spelter Company of
Belgium, who have installed a very complete up-to-date ore-
dressing plant. The ore produced at these mines, and at one
or two other North Country mines, is shipped chiefly to Belgium
for treatment. The total weight of British zinc ore exported
from the United Kingdom in 1913 was 13,378 tons, of which
amount 11,260 tons were consigned to Belgium and approxi-
mately 2,000 tons to France.

In 1912 the total export of zinc ore was 11,139 tons. The
ownership and working of the British mines by foreign companies,
and the exportation of the ore to foreign smelting centres, are not
very creditable to the British mining industry, especially when
it is remembered that practically all the zinc ore smelted in this
country is imported from abroad. Thus in 1913 the total
imports of zinc ores by British smelters amounted approximately
to 65,000 long tons, which were derived mainly from Australia,
Italy, Algeria, Germany, Spain and France.

Attention is now being directed to the possibility of developing
the sources of zinc ore in the British Isles, which, with the applica-
tion of modern methods of dressing and bold development, aided
by adequate financial support, may yet be profitably worked.
The Development of Mineral Resources Department, recently
appointed by the Government, is making a move in this direction.

Canada. — Deposits of zinc ore occur in many parts of Canada
and British Columbia, but at present the output is not large.
Recent proposals for fostering, by the Government, the zinc
industry in the Dominion of Canada will doubtless facilitate
the exploitation of known deposits and the search for new
deposits.

Practically the whole output in the past has come from British
Columbia, mainly from the Kootenay district.

The deposits are numerous, but the ores, which consist of
mixtures of argentiferous galena and blende, with or without
iron and copper pyrites, are complex and difficult to utilise.
Up to the present the zinc concentrates resulting from the
treatment of the ores have been shipped to the United States
for smelting.

There are prospects, however, that in the near future the
ores will be treated in Canada, since the investigations carried
out by the Dominion Government on their treatment by electro-
lytic and other methods have met with some success.

ZINC ORES AND THEIR SOURCES OF SUPPLY

During 1913 Canada produced approximately 11,000 tons of
zinc ore, almost all of which was raised in British Columbia.

In 1914 the output was approximately 13,000 tons, and in
view of the increased mining activity the present output is
probably greater.

Australia. — The well-known deposits at Broken Hill, New
South Wales, are the most important sources of zinc ore in the
British Empire. The ore, which is highly argentiferous, consists
of a complex association of galena and blende, with a gangue
mainly composed of rhodonite, quartz and garnet.

The ore is crushed and submitted to concentration and separa-
tion processes which give two main products, viz., a lead ore
concentrate containing 65 per cent, of lead, 6 per cent, of zinc,
with varying quantities of silver, and a zinc concentrate con-
taining about 46 per cent, of zinc and 8 per cent, of lead with
some 15 ounces of silver per ton. Except for the ore smelted at
the plant of the Broken Hill Proprietary Company at Port Pirie,
South Australia, and about 20,000 tons annually exported prior
to the war to England for treatment, the whole of the zinc
concentrates in the past have been sold under long-term contracts
to smelters on the Continent. Formerly the ore was worked
only for lead and silver, the zinc being neglected, and, as pre-
viously stated, it was estimated that in 1903 zinc residues and
tailings, containing i8'6 per cent, of zinc, and amounting approxi-
mately to 6,000,000 tons, had accumulated at Broken Hill,
besides large quantities which had been used for stope fillings
in the mines.

After many experiments, these accumulated tailings have,
through the application of flotation processes of concentration,
become a very substantial source of supply for the world's zinc.
The first effect of the introduction of flotation processes on the
world's supply of spelter was felt in 1904, and in 1906 the
great rise in Broken Hill zinc production began. Between the
years 1906 and 1911 the production rose from 100,000 tons of
zinc concentrate to roughly 500,000 tons, at about which figure
the annual output has since remained. Owing mainly to the
high price and scarcity of skilled labour, it has not hitherto paid
to smelt these concentrates to any extent locally, or even in the
country ; they have been bought by European smelters and
mainly shipped to Belgium, Germany and France for
treatment.

THE ZINC INDUSTRY

The ascertained life of the chief Broken Hill producing mines
is such as to assure the future production, although on a gradually
reduced scale, for some years to come — probably ten as a
minimum — even if no further ore bodies be developed.1

Since the outbreak of war the shipments of concentrates has
been largely suspended, and the mine owners have had to seek
new markets for that very considerable portion of ore that was
formerly shipped to the Continent, the contracts with the German
firms having been cancelled. Further reference to this matter
will be found on p. 200. As stated above, in normal times the
output of zinc concentrates is approximately 500,000 tons
annually, sufficient to satisfy approximately one-fifth of the zinc
requirements of the world in pre-war times. In 1914 the
output amounted to only 359,310 tons, being 147,350 tons less
than that of the previous year and representing a fall in
value of more than £500,000.

Tasmania. — Lead-zinc sulphide ores occur in the Mount Read
district on the West Coast of Tasmania, and although somewhat
complex in nature the deposits are being developed with a view
to the extraction of the zinc by electrolytic methods, experiments
on a commercial scale having proved the feasibility of such
treatment. Mount Read is about 17 miles by rail from Zeehan
and about 71 miles from the port of Burnie. The zinc-lead
sulphide deposits occur over a length of 7 miles and contain from
24 to 43 per cent, of zinc.

Tasmania is expected to play an important part in future
development in Australian zinc production.

India. — Large and very promising deposits of silver-lead-zinc
ores of the sulphide class occur in Upper Burma. They are
situated at Bawdwin in the Northern Shan States, some sixty
miles from the Chinese province of Yunnan. The deposits are
remarkable for their high silver ratio, and were long ago worked
for that metal by the Chinese.

The ore is complex and consists of galena, blende and pyrites
with occasional chalcopyrite. The crude ore, as mined, is remark-
ably free from gangue and frequently contains, as much zinc as
the Broken Hill concentrates, with substantially greater
quantities of lead and silver.

The deposits are being actively developed, and although up
to the present they have had little influence on the world's supply
1 J. C. Moulden, op. cit., p. 502.

ZINC ORES AND THEIR SOURCES OF SUPPLY

of zinc, there is a prospect of this district becoming an important
producer in the near future.

South Africa. — A lead-zinc deposit — the Rhodesian Broken
Hill — which is reported to be of great prospective importance
has been discovered in North- Western Rhodesia. The rich
oxidised surface ore consists of a mixture of carbonate of lead
with carbonate and silicate of zinc.

The separation of the oxidised ore minerals from one another
presents difficulties which have not yet been overcome. But
when a commercial process has been worked out and transport
facilities have been improved, this, like the Bawdwin deposit,
promises to become a valuable addition to the Imperial lead-zinc
resources. The deposit is being developed, and a smeltery for
lead and zinc is reported to be in course of erection.

The production and value of zinc ore in the British Empire
and in foreign countries for the three years 1911 to 1913 are
shown in the table on p. 56.

European Sources of Zinc Ores 1

The working of zinc ore in Europe in modern times dates
from the introduction of the use of brass, and there are records
extant which show that in 1439 the calamine mines of Vieille
Montagne had been worked for a considerable time by the men
of Aix-la-Chapelle.

In the past Europe has contributed very considerable amounts
to the world's supply of zinc ores, and although the supply is
less than formerly the output is still very large. The bulk of the
ore is mined in Germany, and for many years past this country
has ranked second only to the United States as a producer not
only of zinc ore, but also of spelter. The zinc ore-producing
countries of Europe are here referred to in alphabetical order.

Austria-Hungary. — The more important zinc ore deposits
are situated in Southern Carinthia, Styria and Tyrol.

The Carinthia deposits are distributed over a wide area, and
consist mainly of blende and galena, although large masses of
zinc carbonates occur in certain localities, notably at Schneeberg.

In Tyrol, zinc blende has been mined since 1866, prior to which
the mines were worked for lead only.

In 1913 the total output of zinc ore in Austria amounted to

1 The author is indebted to the Bulletin of the Imperial Institute, 1915,
vol. xiii. for useful information contained in this section.

INDUSTRY

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ZINC ORES AND THEIR SOURCES OF SUPPLY

31,000 long tons ; of which about one-half was devoted to
Government use. The annual output has remained about the
same for the past five years.

Hungary cannot be classed as a zinc ore producer, as mining
for the metal is almost unknown.

Belgium. — In the early days of the zinc industry Belgium was
an important producer of zinc ore, but since 1856 the output has
been comparatively insignificant, owing to the gradual exhaustion
of the rich deposits.

The most important zinc mines are at Bleyberg, and near
Verviers and Liege, whilst the famous deposits worked by the
Societe de la Vieille Montagne are, as previously stated, situated
in Moresnet.

The Bleyberg ore consisted chiefly of zinc blende and galena
in nearly equal amounts, whereas the deposits of Vieille Montagne
consist chiefly of smithsonite and hemimorphite, but large masses
of the silicate, willemite, are also occasionally found. Very little
zinc blende accompanies these ores. Zinc ore has also been
mined at Welkenrodt near Altenberg, Nouvelle Montagne,
Corphalie near Liege, and Philippeville, from which districts
large quantities of ore have been mined in the past.

The present output of zinc ores (entirely blende) from the
Belgian mines is about 11,000 long tons per annum.

Bulgaria. — This country is a small zinc ore producer, the chief
source being the Sedmolchisleniza Mine, about six miles south-
west of Vratza. The crude ore contains about 18 per cent, of
zinc, but by hand-picking the zinc content can be raised to 28
per cent.

Ores are also worked at Roupio and at the Blagodat Mine near
Kustendil.

France. — This country first became a zinc ore producer about
1870, the ore consisting chiefly of carbonate, being obtained
from the country between the Alps and the Pyrenees. Within
recent years the supply of zinc ores has fallen considerably.
The largest producing mines at present are those of Malines
(Gard), where zinc ores have been worked since 1883. Both
oxidised ores and blende are worked.

In the Pyrenees, zinc ores occur in many localities. Argenti-
ferous sulphides and carbonates of zinc and lead are produced
at the Sentein mines in Ariege, and important deposits also
occur in both the Hautes and Basses Pyrenees. Deposits of

THE ZINC INDUSTRY

zinc carbonate, silicate, and blende occur in the department of
Var, the chief mine being the Bormettes, which produces zinc
blende. The total output in 1913 amounted to only about
45,000 long tons, compared with 95,000 long tons in 1909,
more than one-third coming from the mines at Malines.

The French colonies Algeria and Tunis are also important
zinc ore producers and may be conveniently considered here.
In Algeria, both zinc carbonate and blende are worked in the
department of Constantine. The chief mines are the Hammam
N 'Bails and Ain Arko. Ore is also mined at several places near
the Atlas Mountains. In 1913 Algeria produced 81,000 long
tons of zinc ore, chiefly calamine, compared with 83,000 long
tons for the previous year.

Tunis produces about 35,000 long tons of zinc ore annually,
consisting chiefly of carbonate and silicate, derived from a
number of localities. The ore is usually calcined locally before
being exported in order to save freight.

In the past, most of the ore produced in Algeria and Tunis
was shipped from the ports of Bona and Sousse, and found its
way to smelters in Belgium, France and Germany.

Germany. — This country is the chief producer of zinc ore in
Europe, the most important deposits being situated in Upper
Silesia, whilst ore in smaller quantities is obtained in Rhineland,
Westphalia, Nassau, the Harz, etc. Although mined for cen-
turies, the German zinc deposits still produce a considerable
amount of high grade ore.

The well-known deposits of Upper Silesia occur in the south-
eastern corner of the province, on the borders of Austria and
Russia. The ores of this district are principally calamine and
blende. The latter occurs in the deeper workings, consequently
as the mine workings increase in depth the proportion of calamine
as compared with blende has gradually declined.

The calamine occurs rarely in the condition of pure zinc
carbonate ; the bulk of the ore is in the form of a dolomitic
calamine, often more or less argillaceous. The deposits are very
irregular, and occur in the form of more or less extensive pockets,
whilst the blende deposits show great continuity.

Oxidised ores were treated exclusively in the Silesian district
until about 1860, but since that time blende has been worked in
increasing quantity and is now by far the more important ore
smelted in the district.

ZINC ORES AND THEIR SOURCES OF SUPPLY

The crude zinc blende, as sent to the dressing plants, contains,
on the average, about 10 per cent, of zinc, but dressing gives a
high-grade smelting concentrate.

The calamine produced in Upper Silesia is usually ferruginous
and of high grade, containing from 28 to 35 per cent, of zinc ;
cadmium in appreciable quantity is usually present. Ores
containing as little as 13 per cent, of zinc are worked in Silesia
by local smelters, such ore being of too low grade to bear the cost
of transport. As a general rule, the zinc ores smelted in Silesia
are of very low grade.

In Westphalia, the ore is mainly blende, the chief deposits
occurring at Iserlohn and Brilon.

In the Upper Harz and Hanover, zinc blende is recovered in
the dressing of argentiferous lead ore mined near Clausenthal
and Laurenthal.

In the Lahn Valley, Nassau, important deposits of more or
less complex sulphide ores occur, carrying about 3 per cent, of
zinc, 4 per cent, of lead, and 2 oz. of silver per ton.

The crude ore is concentrated at the Laurenberg, Silberau and
Friedrichssegen works, and yields a blende concentrate containing
44 per cent, of zinc, and a galena concentrate with 36 per cent, of
lead and n oz. of silver per ton.

The Lower Harz deposits occur chiefly at Rammelsberg, near
Oker. The ore is an intimate mixture of zinc blende with other
metallic sulphides, and yields on concentration a product carrying
25 per cent, of zinc.

Special processes have been devised for the treatment of the
Rammelsberg ore body (see p. no).

At the present time, the larger proportion of the zinc ore
mined hi Germany comes from the Silesian district, the output,
which has steadily declined in recent years, amounting to
between 650,000 and 700,000 long tons per annum. In 1913
the production amounted to 627,000 long tons, a decline of about
10,000 tons on the previous year. This decrease in output is,
however, most probably intentional, since Germany, as previously
stated, has for some years adopted the policy, which is being
strictly followed, of conserving national resources of ore. It is
due to this fact that Germany has been able to maintain a
considerable output of zinc during the war, in spite of the cutting
off of imported ores.

Greece. — The most important zinc mines are those of the

THE ZINC INDUSTRY

Laurium district, where both zinc blende and carbonate occur.
The mines are of great antiquity and still yield a considerable
amount of ore. The carbonate ore is usually calcined before
export, and then contains about 60 per cent, of zinc. The
production in 1913 consisted of about 30,000 long tons of blende
and 20,000 long tons of calcined calamme a total of 50,000
long tons, showing a decrease of some 17,000 long tons on the
previous year.

Italy. — Zinc carbonate ore is mined chiefly in Sardinia, the
carbonate of which has long been famous. The mines now
worked are amongst the most productive in Europe. Less im-
portant deposits occur in Lombardy, Piedmont and Tuscany.
The richest mines in Sardinia are probably those of the Inglesias
district, which yield zinc carbonate and silicate near the surface,
whilst zinc blende is found at the lower depths.

The output was approximately 151,000 long tons in 1913.

The ore has hitherto been exported chiefly to Germany, Belgium
and the United Kingdom. Important zinc mines in Sardinia
have long been operated by the English Crown Spelter Company,
of Swansea, to which port the ore is shipped for treatment.

Norway. — Small amounts of zinc ore have been mined at
Hadeland, Modum, and Ranen. Extensive deposits of low-
grade ore occur near Christiania, but their concentration has
presented considerable difficulty.

Russia. — Russian Poland, in the districts bordering on Silesia,
produces calamine from deposits which are probably an exten-
sion of the Silesian deposits in Germany. At one time the zinc
deposits of Poland were amongst the most productive in
Europe.

Several deposits of complex ore containing zinc occur in the
Nerchinsk district of Eastern Siberia, and in the Altai Mountains,
Siberia, in the Irtish River district. These districts are being
developed, with the aid of British capital, and promise to
become of importance in the future.

In the Northern Caucasus, rich deposits occur at Sadon and
Primorsk, the latter being mined by the Tetysch Company.

The output of the district in 1910 was about 20,000 tons.

Spain. — The most important zinc ore deposits are found in
the provinces of Murcia and Santander, which produce about
80 per cent, of the total Spanish output.

Small amounts are obtained from deposits in the provinces

ZINC ORES AND THEIR SOURCES OF SUPPLY

of Teruel and Cordoba. About 175,000 long tons of ore, both
cal-amine and blende, are mined annually in Spain, a small portion
only of which is smelted in Spain, the remainder being shipped
to Belgium, Germany and France.

Sweden. — The only important mines appear to be those at
Ammeberg, in the Nerike province. The mines, which are
controlled and worked by the Vieille Montagne Company, are
situated about eight miles from Ammeberg, at the northern end
of Lake Wetter. The ore consists of zinc blende, associated
with pyrites and galena, and after hand-sorting carries about 20
per cent, of zinc and i per cent, of lead.

In order to facilitate the removal of the pyrites the ore is slightly
roasted before being crushed and concentrated. The concentrates,
as shipped, contain about 42 per cent, of zinc, and have hitherto
been treated in Belgium.

The output in 1913 was 50,840 long tons, practically the whole
being blende.

Moulden has stated that many of the iron mines yield also no
small amounts of zinc blende, and under favourable conditions
the potentialities of this country are undoubtedly considerable.

American Sources of Zinc Ore

The United States of America is the greatest producer of zinc
ores in the world, the output at the present time far exceeding
that of any other country.

The output in 1913 approximated to no fewer than 790,000
long tons, exclusive of ore exported or used for the manufac-
ture of zinc oxide. Since the outbreak of war the output has
increased enormously.

Both calamine and blende are extensively worked, in addition
to the zincite and franklinite deposits. There exist also great
reserves of the more complex low-grade lead-zinc ores, which,
owing to the abundance of richer and purer ores, have not
yet been exploited to any considerable extent.

Of the recoverable zinc content of the ores mined in 1913,
more than 77 per cent, was contained in zinc ores proper, the
remainder, with the exception of 0-8 per cent., being from zinc-
lead ores.

The chief ore-producing States in order of importance are
Missouri, Wisconsin, Idaho, Kansas, Oklahoma, Colorado and

THE ZINC INDUSTRY

Montana, but there are in addition some twelve other States
that produce smaller quantities of zinc ore and collectively
considerably augment the output for the United States.

The mine production of zinc-yielding ores in 1913 from the
more important States is shown in short tons (2,000 Ib.) in the
following table : —

ZINC ORE PRODUCTION IN THE UNITED STATES, IN SHORT
TONS (2,000 LB.), IN 1913. x

Zinc Ore.

Zinc-lead Ore.

State.

Crude

Zinc

Crude

Zinc

Total.

Ore.

Content.

Ore.

Content.

Short tons.

Per cent.

Short tons.

Per cent.

Short tons.

Missouri

8,049,300

1-6

— ,

—

8,049,300

Wisconsin

1,406,000

2-1

— .

— ,

1,406,000

Idaho

2,719

42-2

646,080

1-6

648,799

Kansas

590,300

1-7

— .

— ,

590,300

Oklahoma

581,000

2-0

— ,

581,000

New Jersey

490,434

17-2

— ,

— -

490,434

Colorado

141,295

23-5

203,367

11-4

344,662

Montana

3,840

9-8

307,615

I4'3

3H,455

'~tTtah . .

16,322

29-2

211,609

2-1

227,931

Tennessee

171,392

3'3

— .

— ,

171,392

New Mexico

40,439

17-0

8,735

16-1

49,174

Arizona

14,554

17-2

29,700

7'3

44,254

Nevada

10,208

31-1

16,749

24-1

26,957

Totals . .

11,517,803

1,423,855

12,941,658

These figures show that the zinc content of the ores as mined
varied from as little as 1-6 per cent, to 42 per cent., these figures
being the average for Missouri and Idaho respectively ; the
average for the whole of the crude zinc ore mined in 1913 was
2-8 per cent.

The low-grade ores are submitted to concentration processes,
and so far, in the United States, the greatest tonnage of zinc
concentrates has been produced by magnetic separators, without
including the enormous separating plant at Franklin Furnace,
New Jersey, with its capacity of nearly one thousand tons
daily, for the separation of franklinite from willemite. Flotation
processes are, however, now being introduced for the treatment

1 United States Geological Survey and Department of Mines Report,
1914.

ZINC ORES AND THEIR SOURCES OF SUPPLY

of complex ores in America . Detailed reference must be restricted
to the more important zinc ore-producing States in their order
of quantity of ore mined.

Missouri. — Output 8,049,300 short tons. Although the zinc
deposits of Missouri consist of some of the lowest grades of zinc
ores worked in the country, the enormous output enables the
State to hold the first place as regards zinc production. The
ore mined is mainly zinc blende with small quantities of galena
and marcasite.

About three-quarters of the celebrated Joplin district is in
Missouri, the remainder being in Kansas (Cherokee County)
and Oklahoma (Ottawa County).

The zinc-bearing deposits of the Joplin district consist of large
pockets from which ore can be removed cheaply and in a more
or less crude manner.

The character of the ore is such that, in practically all cases,
it breaks away from the gangue material easily with coarse
crushing, and makes an ideal jig product, any lead contained
in the crude ore being saved by the jig as a separate product,
which is sent to the lead smelter. The bulk of the ore now mined
in this district is blende, calamine forming about one-tenth only
of the total output.

Important deposits of " silicate ore " (a mixture of hemimor-
phite and smithsonite) occur in the Aurora and Granby districts ;
in many cases the ore contains from 40 to 45 per cent, of zinc,
and is therefore of sufficiently high grade to ship in lump form.

Wisconsin. — Output 1,406,000 short tons. As a zinc ore
producer this State ranks second, but occupies fourth place as
regards zinc output. The most important ore-producing counties
are Grant, Iowa, and Lafayette.

The ores, which consist of galena, zinc blende, and smithsonite,
contain a large amount of marcasite, and much difficulty was at
first experienced in concentrating the ore, but this has been
overcome by slightly roasting the ore to render the marcasite
non-magnetic.

By this means magnetic separation of the blende from its
associated iron sulphide is rendered possible, thus giving a shipping
ore of sufficiently high grade suitable for distillation. In 1914
there were 46 ore dressing mills and five magnetic separating
plants in operation in various places in the Wisconsin district.

Zinc carbonate ore also occurs in Wisconsin, mainly in the

THE ZINC INDUSTRY

Highland and Mineral Point districts, and it is chiefly used for
the production of zinc oxide.

Idaho. — Output 648,799 short tons. Zinc-lead ore is chiefly
mined in this State and is obtained from the Beaver, Hunter and
Placer Center districts of Shoshone County.

The zinc content of the ore as mined is about 2 per cent., but
concentration yields a product containing on an average 34 per
cent, of zinc and small amounts of gold and silver, which enhance
the value of the ore.

A small quantity of crude ore of good quality and containing
about 42 per cent, of zinc was shipped from the Beaver, Summit
and Lelande districts in 1913.

Kansas. — Output 590,300 short tons. Practically the only
deposits at present being worked in this State are those of
Cherokee, in the south-eastern part of the State, which forms
the western portion of the Joplin district.

Both carbonate and sulphide of lead occur with the zinc ores,
which are of low grade and contain on an average about 1-7 per
cent, of zinc only.

Oklahoma. — Output 581,000 short tons. The zinc ore deposits
in Ottawa County in this State form the south-western portion
of the Joplin district. The Miami district is responsible for
about 95 per cent, of the total output in Oklahoma. The crude
ore as mined contains a little more than 2 per cent, of zinc, but
yields a concentrate suitable for smelting.

New Jersey. — Output 490,434 short tons. This State is of
considerable interest on account of the special nature of the
zinc minerals in the ore.

Practically the whole of the output is obtained from two
deposits that occur in Franklin Furnace and Stirling Hill, in
Sussex County, both of which are mined by the New Jersey
Zinc Company. Enormous quantities of the ore are consumed
annually in the manufacture of zinc oxide direct from the ore,
so that in 1913 New Jersey only attained fifth place on the
basis of zinc produced.

The ore comprises zincite, willemite and franklinite, but the
relative amounts of the minerals vary considerably. The
franklinite is usually closely associated with the other zinc
minerals, from which it is separated by magnetic treatment, first
devised by Samuel Wetherill, who also developed and applied
the blowing-up grate furnace for the economic production of

ZINC ORES AND THEIR SOURCES OF SUPPLY

zinc oxide direct from these ores. The name of Wetherill thus
became intimately associated with the history and success of the
district.

Colorado. — Output 344,662 short tons. Zinc ore is mined in
many localities in this State. About 80 per cent, of the zinc
ore produced in the State is derived from the Leadville mines
in Lake County. The deposits yield galena, zinc blende, and
iron pyrites, the crude ore containing 19 per cent, of zinc.
Considerable amounts of zinc carbonate and silicate are also
mined in this district. In 1913 the output consisted of approxi-
mately 98,000 tons of crude sulphide ore and 136,000 short
tons of carbonate and silicate ore.

The next largest producing counties are Eagle and Summit,
their total output in 1913 being about 8 per cent, of that of the
whole State. In Summit County zinc blende is associated with
galena, but usually the quantity of galena is small. The ore as
shipped is stated to contain 42 per cent, of zinc.

Other zinc ore-producing counties are San Miguel, Dolores
and Chaff ee.

Montana. — Output 311,455 short tons. The zinc ore produced
in this State comes largely from the celebrated copper district
of Butte, the chief mines being the Butte and Superior. The
Butte district, which has very rapidly come into prominence as
a zinc ore producer, promises to become one of the largest zinc-
producing areas in the United States.

The ore is chiefly zinc blende and carries about 20 per cent,
of zinc, but by concentration a product is obtained carrying
49 per cent, of zinc and about 24 oz. of silver per ton and a little
gold. In 1913 Montana was third as a zinc produces*^

Utah. — Output 227,931 short tons. The ore produced in 1913
was derived chiefly from Beaver County, whilst important out-
puts were made from the counties of Salt Lake, Utah, Wasatch,
Summit, Tooele and Juab.

The zinc-lead ores contained on an average about 27 per cent,
of zinc and 0-06 oz. of silver per ton, but concentration yielded
a product containing about 33 per cent, of zinc and nearly 2 oz.
of silver per ton.

Tennessee. — Output 171,392 short tons. During the past few
years there has been considerable activity in prospecting zinc-
bearing deposits in Eastern Tennessee, and several large bodies
of ore have been located.

65 F I

THE ZINC INDUSTRY

Zinc blende is mined in Knox County, the zinc content of the
crude ore being from 3 to 5 per cent ; the concentrate obtained
from this carrying about 60 per cent, of zinc.

New Mexico. — Output 49,174 short tons. The production in
1913 was chiefly from mines in the Socorro, Luna and Grant
Counties. The ore shipped in 1913 consisted of 12,000 short
tons of zinc blende and concentrates containing 42 per cent,
of zinc, and 13,000 short tons of carbonate ore containing 34
per cent, of zinc.

Arizona. — Output 44,254 short tons. Most of the ore mined in
this State is obtained from Mohave and Pima Counties. Small
amounts are also produced in Yavapai and Cochise Counties.
Both zinc and zinc-lead ores are produced, the latter forming
about two-thirds of the total output.

Nevada. — Output 26,957 short tons. The ore raised in this
State in 1913 consisted of zinc-lead ore and of silicate and
carbonate ; it was chiefly produced in Clarke and Lincoln
Counties. The ore as sold to the smelter averaged about 30 per
cent, of zinc.

Mexico. — Zinc ore occurs in a number of localities in Mexico,
but many of the deposits cannot be utilised owing to transport
and other difficulties.

The chief producing States are Coahuila, Chihuahua, San Luis
Potosi, Tamaulipas and Nuevo Leon.

The bulk of the ore mined in the past has been exported to
America and to Europe, but in recent years the unfortunate
political disturbances prevailing in the country have prevented ore
producers from taking advantage of the more favourable import
duties on ores entering the United States.

Conditions limiting the shipment of zinc ore from Mexico have
now improved somewhat, so that a larger output of ore than in
past years is to be expected.

In 1909 the ore imported by America from Mexico amounted
to 105,000 short tons, but since that time the output has fallen
considerably, amounting to only 18,000 short tons in 1913 and
21,000 short tons in 1914.

The ore shipped usually contains from 30 to 40 per cent, of
zinc and varying amounts of silver.

South America. — This continent is at present a very small zinc
ore producer, Bolivia and Peru alone making small contributions.

Bolivia. — The present output is derived chiefly from the

ZINC ORES AND THEIR SOURCES OF SUPPLY

Huanchaca district, but zinc ores have been found in a number
of other localities in Bolivia.

Owing to shortage of water for concentrating the ore and to
other difficulties, the output has decreased in recent years. The
production in 1913 was 7,500 short tons, and in 1914 it had
decreased to approximately 4,000 short tons.

An estimate of the total production of zinc ore in the United
States is given in the report of the zinc smelters, who are stated
to have smelted in 1914 approximately

629,000 short tons of blende.
227,000 ,, ,, of calamine.

Total . . 856,000 short tons.

This total will probably include some 21,000 short tons of ore
imported from Mexico and 11,000 short tons from Canada.

On the other hand, a small quantity of ore, amounting to
11,000 short tons, was exported to Europe.

The very considerable increase of zinc ore production in America
since the outbreak of war is shown by the following figures, which
give the recoverable zinc content of the ore mined in the United
States for the past four years.1 In 1913 it was 406,000 short
tons ; in 1914, 407,000 short tons; in 1915, 605,915 short tons,
and in 1916, about 708,000 short tons. The large increase in
output in 1915 and 1916 was due to the demand for zinc from
Great Britain and the Allies.

The largest increase in output was made by the Joplin region,
which in 1916 had an increase of more than 40,000 short tons.
Montana made a notable increase and from the return available
appears to have taken second place. Substantial increases were
also made in the zinc mining districts of the Upper Mississippi,
Valley, Colorado, Tennessee, Idaho, Nevada, New Mexico, New
York, Arkansas and Washington.

Of the total output of zinc in the ore mined, the Eastern States
produced 148,000 short tons, or 21 per cent. ; the Central
States 274,000 short tons, or 39 per cent. ; and the Western
States 286,000 short tons, or 40 per cent.

Asiatic Sources of Zinc Ores

Little accurate information appears to be available regarding
the nature and extent of many of the zinc deposits in Asia.
1 United States Geological Survey Report.

67 F 2

THE ZINC INDUSTRY

Actual figures of output are also very difficult to ascertain.
China has long been the largest zinc ore producer in Asia, but in
recent years considerable attention has also been given to zinc
deposits in Japan and Siberia.

China. — 'This country appears to have been the world's earliest
producer of zinc ores, and also of metallic zinc produced by
crude methods of native smelting.

The most important deposits worked are situated in the Pre-
fecture of Changlin, in Hunan province, and consist of argenti-
ferous galena, associated with blende, iron pyrites and calcite.
The deposit has been exploited by means of surface workings
for about two centuries, and has been considerably developed
during recent years as the result of German influence. The
chief mines are the Shui K'ou Shan, worked by the Hunan
Board of Mines.

A considerable portion of the ore mined is first submitted to a
preliminary dressing at the mine. The dressed blende and mixed
zinc-lead sulphides are then sold to a German firm having an
ore-dressing plant at Woo Chang, where the material is further
concentrated to yield a zinc concentrate carrying from 30 to 35
per cent, of zinc, which prior to the war was exported to Germany
to be smelted.

It is stated that before the outbreak of war the German
company was considering the desirability of erecting a smeltery
in China. The output of zinc ore in 1914 was approximately
21,500 long tons.

Numerous deposits of zinc ore are known to occur also in
South-Western China, and in Kweichow province appreciable
quantities of metallic zinc have been produced by native
smelting.

Japan. — Zinc blende, usually associated with ores of copper
and lead, has been found in a number of localities in Japan, but
up to the present most of the marketable ore has been obtained
from the Kamioka Mines in the province of Hida, the output
of crude ore being normally about 10,000 long tons annually.
The crude ore, consisting of zinc blende and argentiferous galena
carrying from 10 to 16 per cent, of zinc, is treated at two dressing
works at Shikama and Mozumi, where wet concentration and
flotation methods are employed. The greater part of the zinc
concentrates produced have in the past been exported, chiefly
to Belgium.

ZINC ORES AND THEIR SOURCES OF SUPPLY

The lead concentrates are smelted in blast furnaces about
35 miles from Toyama.

Zinc mines of less importance occur in the provinces of Tsu-
shima, Etchu, Echizen, Bizen and Mimasaka.

The output of zinc ore within the Japanese Empire has shown
a very marked increase during recent years, practically the whole
of which has been exported to foreign smelting centres for treat-
ment. Thus the exports amounted to approximately 18,000
long tons in 1909, to 22,000 long tons in 1910, and 23,000 long
tons in 1911. The annual production at the present time is
said to be about 50,000 long tons.

Japanese zinc ore amounting to 1,200 long tons was imported
into the United Kingdom in 1913 and more than 5,000 long tons
in 1914.

In view of the great activity in the Japanese zinc industry
since the outbreak of war, and the erection of smelting plant to
smelt the zinc ores mined in the country, the mine-owners would
appear to have a very hopeful future before them.

Siberia. — Important deposits are worked at the Ridder Mine
in the Altai Mountains, Siberia. Since the mine was acquired
by the Irtish Corporation, Ltd., in 1915, considerable develop-
ment has taken place. The ore produced is said to consist of
two qualities, about one half being high-grade ore containing
27 per cent, of zinc, 18 per cent, of lead, and I oz. of gold per ton.
whilst the remainder is of lower grade, carrying about 9 per cent,
only of zinc and 5 per cent, of lead. As previously stated, the
Irtish Corporation are building a large zinc-and-lead smelting
plant at Ekibastus for the treatment of the ore of the Ridder
Mine. Part of this plant began operations in May, 1916.

CHAPTER IV

THE MARKETING OF ZINC ORES

The Concentration of Zinc Ores

ORES of zinc as mined are seldom of sufficiently high grade
to be sent direct to the smelter for immediate conversion into
metal without previous concentration. Especially is this the
case with ores containing zinc blende, which is by far the most
important source of zinc at the present time.

The gradual exhaustion of the deposits of rich calamine ores
has led, during the past few decades, to a considerable develop-
ment in the concentration of zinc blende ores to meet the demand
of the smelters for high-grade ores.

During the past twenty years the zinc ore market has been
considerably augmented by the supply of thousands of tons of
" zinc concentrate," a high-grade zinc blende product resulting
from the mechanical treatment of low-grade ores, and so-called
complex ores, in which the zinc is intimately associated with other
metals, such as lead, copper and silver.

The preliminary treatment of zinc ores has for its object not
only the enrichment of the ore by removal of the minerals of
comparatively low specific gravity which compose the gangue,
but also the elimination, as far as possible, of heavy minerals,
such as those containing lead, iron and manganese, which are
objectionable in smelting.

In many cases these heavy minerals are of market value and
are recovered in sufficient quantity to be a source of profit.

The methods of concentration employed include hand sorting
and separation by gravity (wet dressing), electromagnetic and
oil flotation processes, or combinations of these. The process
adopted varies with the nature of the ore.

Where ores are sufficiently high in zinc blende and lead

THE MARKETING OF ZINC ORES

(galena) and carry little or no iron pyrites, or chalcopyrite, the
ordinary methods of water concentration in jigs, and upon tables,
such as are employed at Joplin and some of the Leadville mines
in the United States, give satisfactory separation, but magnetic
separation or flotation methods are usually employed for more
complex ores. In favourable circumstances, and if worked on a
sufficiently large scale, ore containing as little as 3 per cent, of
zinc may be worked at a profit, and will on concentration yield
a zinc product suitable for smelting ; but in such cases the lead
and copper, and small amounts of silver and gold which often
accompany the zinc in the ore, are recoverable, and are usually
the determining factors of commercial success in the treatment of
low-grade ores.

In this connection, the more modern system of concentration
known as " flotation," which is applicable to the treatment of
the sulphide ores of most metals, has in recent years been widely
adopted for concentrating those of zinc.

Magnetic concentration has been successfully applied to the
separation of the zinc minerals comprising the well-known
franklinite ores of New Jersey.

Following the pioneer work of Wetherill's high intensity
magnetic separator, considerable progress has been made in the
magnetic concentration of ores, and many machines have been
introduced. Electrostatic methods for the separation, by
electric repulsion, of good conductors (such as certain metallic
sulphides, magnetite, haematite, etc.) from poor conductors
(such as silicates, carbonates, oxides and sulphates, and including
zinc blende) were first applied in practice by Blake and Mecher-
nich, and followed by Sutton and Steele, Huff and others.

Magnetic separation of blende and pyrites may be accomplished
without preliminary roasting by the use of high intensity mag-
netic separators of the Wetherill type, the zinc mineral being
lifted out of the mass.

The more usual practice, however, is to give the mineral a
magnetic or " flash " roast, rendering the iron magnetic, after
which it is separated from the mass by separators of the low
intensity type, such as that of Dings.

The main objection to electric separators appears to be their
inability to handle fine powders, and their liability to dust
trouble unless the dust be first removed.

The flotation processes of concentration have come rapidly

THE ZINC INDUSTRY

to the front since their introduction some fifteen years ago by
the Messrs. Elmore. Their work, which resulted in" the filing of
Frank Elmore's patent in 1898, focussed the attention of
metallurgists upon the great possibilities of these methods.

Many new systems of concentration by flotation have been
introduced within recent years.

In these processes advantage is taken of the property possessed
by metallic sulphides, when in a fine condition, of floating in
water, hence their term of " flotation " processes. When
for example, a mixture of such sulphides and waste mineral
(gangue), in a finely crushed condition, is gently brought on to
the surface of moving water, it will be found that the sulphide
particles will float, whilst those of the gangue will break through
the surface and sink. This different behaviour will be aug-
mented if the water be very slightly acidulated, and still more
so if the surface of the sulphide particles is oiled or greased.
Since metallic sulphides possess also the property of absorbing
oil, or being " wetted " by oil, while particles of gangue do not,
a separation can be effected by agitating the finely crushed ore
with water containing a small proportion of oil, whereby the
sulphide particles will gradually collect in the floating film of oil,
whilst the rock particles remain sunken.

Neither of the above phenomena alone suffices for a practical
working method ; other principles equally important have been
drawn upon (such as the modification of the surface-tension of
water, factors of absorption, aeration, fine subdivision of the
mineral, eto.) and blended into one or other of these processes,
which reverse the operations of " wet " concentration inasmuch
as they save the heavier mineral by floating it to the surface
whilst causing the specifically lighter material to sink.

In the Elmore oil vacuum process separation is assisted by the
partial exhaustion of a large metal receiver into which the oiled
slimes and water enter. The air films surrounding the oiled
particles are thus expanded, and the separation is much improved.
In other cases diluted acid is employed, and with suitable ores
gas bubbles are produced which cause the sulphide particles to
rise to the surface of the liquid.

One of the most widely used and successful of the flotation
methods of concentration is that known as the " Froth Flotation
Process," wherein the mineral is recovered in a more or less thick
and coherent bubble-froth which is skimmed or run off from

THE MARKETING OF ZINC ORES

the pulp, thus effecting a separation of the mineral from the
gangue.1

The success of flotation methods has been very marked in
the treatment of large quantities of slimes and complex ores
that had previously defied all known methods of treatment.

They proved to be very suitable for the treatment of
the complex ores obtained from Broken Hill, New South
Wales, in which zinc blende and galena are very intimately
associated, and enormous quantities of these and similar ores
are now treated by flotation.

By gravity concentration it was possible to market only about
60 per cent, of the lead in the Broken Hill deposits, and less of
the silver, leaving the bulk of the zinc associated with the heavy
waste as a middle product, whilst the finest and lightest portion
of the crushed material was often allowed to flow away.

So successful has been the application of flotation methods to
the treatment of the Broken Hill ores that now the whole range
of zinc products is treated by flotation, and zinc concentrate to
the extent of about 500,000 tons per annum is being recovered.

Owing principally to improved methods of mechanical separa-
tion, large deposits of zinc-lead sulphides are being opened up
in America, Burma and Siberia, in addition to those in Australia
and elsewhere.

In view of the fact that the supply of flotation and other zinc
concentrates is bound to increase, metallurgists are giving special
attention to their treatment, since in many cases their very fine
state of division renders some modification of the ordinary
Smelting processes necessary.

The Valuation of Zinc Ores

For technical purposes, zinc ores are divided into two classes :
( i) zinc blende, and (2) calamine, the latter including the common
carbonates and silicates.

A large proportion of the zinc ore now marketed consists
of zinc blende concentrates, which usually contain from 35 to
55 per cent, of zinc.

The market value of an ore is based on the price of the metal
content, less the total cost of extraction ; in other words, the
net return to the proprietors.

The zinc content is determined by wet analysis, usually

1 " Copper, " H. K. Picard, London, 1916, p. 24.
73

THE ZINC INDUSTRY

volumetrically by sodium sulphide (Schaffner's method) or by
ferrocyanide.

The value of a zinc ore depends chiefly upon its content of
zinc and the absence of objectionable impurities such as iron,
manganese and lime (calcium carbonate), which form fusible
slags and increase the corrosion of the retorts ; and lead, cad-
mium, arsenic and antimony, which contaminate the spelter
and therefore lower its market value. Lead, however, is present
in almost all zinc ores.

The total percentage of iron and manganese should not exceed
10 per cent., and if lead is present the metallic zinc produced by
distillation will be contaminated with lead unless special precau-
tions are taken.

Fluorite (calcium fluoride) is sometimes present and is a very
undesirable constituent, as it forms a very fusible slag, and when
present in appreciable quantity in zinc blende causes deterioration
in the lead chambers used in the manufacture of sulphuric acid
as a by-product from the roasting of the ore.

The value of the ore is also affected by its character, whether
oxidised or sulphide, or a mixture of both ; the sulphide ore
must be roasted, but yields a diminished weight for the subsequent
treatment, which is the most expensive part of the process ; the
calamine ores seldom require preliminary treatment by the
smelter, as the economy in freightage between mine and smelter
is usually sufficient to warrant calcination to expel carbon
dioxide and combined water prior to shipment, this saving being
more important where the mine is widely distant from the smelting
worksi

The value of an ore is, moreover, affected by its physical
condition. Lump ore is subject to an additional expense for
crushing : fine concentrates are more expensive and troublesome
to treat than coarse concentrates.

Some ores roast and distil easily, others with more difficulty.
All these factors are considered by the zinc smelter in purchasing
ores.

It will be observed, therefore, that whilst the chemical com-
position of ores is the most important factor in determining
their value, the price does not depend solely on the metallic
content and on the presence of other compounds, but also on
certain physical properties governing the suitability of the ore
for smelting purposes or for other methods of treatment.

THE MARKETING OF ZINC ORES

Several schedules are employed in Europe for calculating the
value of zinc ores, all of which embody at least three factors :
(i) the current price of spelter, (2) the zinc content of the ore,
(3) a " returning charge " per ton of ore.

The last named is the cost of smelting a ton of ore, and is
affected by the mineralogical nature of the ore and its physical
condition. The treatment charges necessarily vary in different
smelting centres, as, in addition to the above factors, they are
also affected by local conditions, such as fuel supply, cost of
labour, freight, etc.

A general type of formula used for calculating the value of
zinc ores is as follows :

Where V is the value in £ per ton,

P the price of spelter (G.O.B.) in London,
T the percentage of zinc in the ore,
R the " returning charge."

The selling price basis for London spelter (G.O.B. = good
ordinary brands) is usually the average of the daily prices for the
month previous to arrival, and is usually taken as London Public
Ledger quotation less 5 per cent., which is, of course, 0-95 P
of the formula. Thus on a £20 average quotation basis the ore
unitage paid for (T - 8) is based on 95 per cent, of £20, which is
£19, or 3-8 shillings per unit.

As an example of the use of the above formula, if an ore which
contains 48 per cent, of zinc and spelter is £30 per ton in London,
and if a returning charge of £3 55. be assumed, then the market
value of the ore per ton will be :

£0-95 x 3o(^8) -& 5 o = £8 3 o.

When silver is present in the ore in sufficient quantity to permit
of profitable extraction, it is usually paid for at the price based
on the current price of standard silver after allowing for smelting
loss and for cost of working.

In determining the treatment charge on the ore purchased,
the zinc smelter starts with the cost of smelting a ton of the ore
of average composition, that is to say, the mixture on which he
proposes to operate his furnaces.

THE ZINC INDUSTRY

For various reasons it is aimed to have all the furnaces on the
same ore-mixture. To this smelting charge he adds the profit
that he ought to make to obtain a proper interest on his invest-
ment, allowing for the necessary amortisation of his outlay in
plant. The further addition of the freight on the ore to his
works, and on the spelter product to its market, with allowances
for the expenses incurred in buying the ore and selling the spelter,
gives the returning charge which he must make against the ore
in buying it on the basis of f.o.b. (free on board at port of ship-
ment) or f.o.r. (free on rail) at the mine or concentrating mill
where produced.

Within recent years a marked change has taken place in the
quality of the ores supplied to the zinc smelter. As the result
of the gradual exhaustion of the high-grade calamine supplies,
and even of the richer blende ores, and also the increasing
demand for zinc, sulphide ores are now readily purchased which
earlier would have found a poor market. It is not long since
50 per cent, of zinc in a blende product was a standard which
admitted of little reduction, particularly amongst smelters in this
country.

For several years prior to the war, however, it was possible
to market ore containing only 35 per cent, of zinc, but as the
price of spelter has advanced considerably since the outbreak of
war, many smelters have refused to buy ores carrying less than
40 per cent, of zinc, in order to secure as large an output of metal
as possible from their furnaces. As a general rule, zinc smelters
consider low-grade ores only if they contain other metals, such
as lead and silver, in sufficient amounts to render the residues,
after extraction of the zinc, profitable commercial sources of
those metals, and thus to recoup the loss due to the decreased
zinc content of the ore. Such foreign metals are, however,
naturally paid for at a low price owing to the incompleteness of
their recovery.

That these secondary sources of profit may nevertheless become
substantial is shown by the fact that, whereas zinc concen-
trates were formerly subject to a deduction or " penalty " by
the smelter for shortage of zinc below a certain figure, and the
ore producer, therefore, did his best to increase the zinc tenor
and to decrease that of lead and silver, he is now subject to a
penalty if the zinc content is above a certain limit when this
involves what the smelters consider to be an undue absence of

THE MARKETING OF ZINC ORES

silver or lead in connection with a given smelting charge. This
applies more particularly to the Broken Hill and similar zinc
concentrates. These zinc blende concentrates contain a payable
quantity of silver, to recover which a certain amount of lead
must be present. Thus the Continental smelters, who formerly
treated large quantities of the Broken Hill concentrate, called
for a product containing not less than 8 per cent, of lead, which
metal they required for collecting the silver when smelting the
residues, although the flotation process is capable of producing
a zinc concentrate much lower in lead if desired.

The European Ore Trade

Owing to the growing shortage of the supply of domestic zinc
ores and the ever increasing demand for zinc during the past 30
years, the European smelters have had to rely more and more
on imported ores, and this resulted in a European ore trade that,
at the outbreak of the war, had grown to considerable dimensions.

For many years, large quantities of zinc ore have been shipped
to Antwerp and to Swansea from Sardinia, Algeria, and Spain,
and also in more recent years from Australia and America.
Despite the growing disposition of the American smelters to
adapt their works to the handling of all classes of ores, the ship-
ment of zinc ores from America to Europe has in the past been
important, and the tendency before the war appeared to be for
the shipments to increase rather than to decline. The American
ore was shipped from Colorado via the Gulf ports of Galveston
and New Orleans, cheap ocean freights being secured on the
steamers carrying cotton to Europe.

The ores were shipped to Antwerp and to Swansea in bulk,
as no sacks appear to be proof against the acid nature of the ore.
The ore arrived in the condition of fines, having generally been
calcined, if calamine, and roasted, if blende, except in the case
of Australian concentrates.

The cargo was sampled by reserving one basket in twenty-five
during unloading, the sample basket being chosen at random
by agreement between the representatives of the buyer and
seller, or, more commonly, the agent to whom both parties had
entrusted their interests in this part of the business. The ore
reserved for sample was reduced in quantity either by machinery
or mixed and quartered down by hand to obtain a small repre-

THE ZINC INDUSTRY

sentative quantity for assay to determine the zinc content and
the presence of objectionable impurities.

Settlements were made in Antwerp and Swansea on the results
of the assay. The ores were bought on different formulae, of
which an example has been given on p. 75.

The formula quoted was used for ores containing 46 per cent,
of zinc or more, and was quoted only on consignments c.i.f.
Antwerp (costs, insurance, and freight paid to Antwerp) .

As already stated, this formula is based on payment for the
metallic content of the ore, less 8 units, 95 per cent, of the London
price of spelter, G.O.B., less a returning charge.

The following approximate figures, making a total of nearly
900,000 tons, show the extent of the European ore trade in
1913 :—

Zinc ore imported into English tons, 2,240 Ib.

Germany . . . . . . . . . . 308,000

Austria-Hungary . . . . . . . . 50,000

Belgium . . . . . . . . . . 300,000

France . . . . . . . . . . 173,000

United Kingdom . . . . . . . . 65,000

To what extent the European zinc ore trade will be resumed
after the war is very difficult to predict.

CHAPTER V

, THE SMELTING OF ZINC ORES

PRACTICALLY the whole of the world's supply of zinc is obtained
by the distillation method in retorts in which advantage is
taken of the volatility of the metal at a bright red heat.
Until quite recent years this was the only method of zinc
production, but at the present time appreciable and increasing
amounts of the metal are being produced by wet processes, and
by electrothermic smelting.

Preliminary Treatment. — For the distillation method the first
clearly-defined stage is the conversion of the zinc compounds
present in the ore into oxide by calcination or by roasting, and
this is followed by the reduction of the oxide to metal by means
of carbon at a temperature which is higher than the boiling
point of zinc, i.e., about 940° C. (Moissan).

These two operations are so distinct that they may be, and
often are, carried out for commercial reasons in establishments
widely distant from one another.

The processes of calcination and roasting are different in their
operation, but both aim at the same type of product, i.e., zinc
oxide that is reducible under the conditions of distillation.

Calcination. — Calcination is used for the expulsion of carbon
dioxide and water from carbonate ores, and of water from
hemimorphite ; it also renders the ore more porous, and therefore
more readily acted upon by the carbonaceous matter employed
for its reduction.

Although it is possible to reduce zinc carbonate without
previous treatment, this practice is seldom adopted, as it has been
found more economical to calcine the ore first. Apart from any
other reason, the economy in freightage between mine and
smelter, as previously stated, is usually sufficient to warrant

THE ZINC INDUSTRY

calcination, the saving thus effected being of increasing im-
portance the more widely apart the two are situated.

Calcination is a simple operation, and analogous to the burning
of limestone for lime, being carried out in practically the same
manner, usually in kilns, in the presence of excess of air and also
of moisture, the two latter points being important for the attain-
ment of a good product.

The use of kilns is restricted to lump ore, or to a mixture of
lump and fines, usually in alternate layers, whereas for finely
crushed ore furnaces either of the reverberatory type, or revolving
cylindrical furnaces with a continuous discharge, of the Oxland
type, are used.

The method of calcination employed in Sardinia, where some
of the most important deposits of calamine exist, may be taken
as typical of the best practice in Europe. The lump ore is charged
into slightly conical, circular shaft furnaces, 6-5 ft. in diameter
at the bottom and varying from 12 to 18 ft. in height. The
heat is supplied either from external grates, or by charging the
furnace with alternate layers of coal and ore. The former
method is preferable, as it avoids the contamination of the ore
with ash from the fuel. The complete dehydration of the
hydrated zinc minerals is readily effected by heating to the
dullest perceptible red heat, but when other carbonates are
present a higher temperature is necessary.

The chief carbonates associated with calamine and the approxi-
mate temperatures required for the expulsion of their carbon
dioxide are as follows T : —

Zinc carbonate . . . . . . 300° C.

Magnesium carbonate . . . . 650° C.

Iron carbonate . . . . x. . 800° C.

Calcium carbonate . . . . . . 812° C.

Owing to the comparatively high temperature required to
decompose calcium carbonate, calamine ores containing a high
proportion of this carbonate are the most difficult to calcine
completely, and they usually retain a sensible proportion of their
original carbon dioxide content.

The calcination of calamine is seldom complete, and when
the ores are contaminated with much calcium carbonate or
magnesium carbonate as much as 15 per cent, of carbon dioxide
may be retained.

1 Ingalls, " Metallurgy of Zinc."
80

THE SMELTING OF ZINC ORES

Roasting. — The desulphurisation of zinc blende is a more
difficult matter than the process of calcination as described above.

It is usually effected on the crushed ore by roasting in the
presence of an excess of air, in shelf furnaces of two or more
shelves. The particles of ore should not exceed 2 millimetres
in diameter. Numerous difficulties are encountered in the pro-
cess, which requires considerable experience on the part of the
man supervising the work. Especially is care necessary to
transform the sulphide as completely as possible into oxide and
at the same time to avoid its passage into the sulphate, as the
latter is reduced to sulphide by carbon, instead of to the metal.

Of all the metallic sulphides with which the metallurgist has
to deal, zinc sulphide is one of the most troublesome to roast
" sweet," i.e., to expel all the sulphur.

It has, however, the advantage of not sintering by heat, so
that in the process of roasting it may from the first be exposed
to a higher temperature than most other metallic sulphides.
The roasting is considerably complicated by the presence of other
metallic sulphides, such as those of iron and lead, and by the
presence of manganese, lime, strontia and barytes. The first
effect of the elevation of the temperature in roasting is to distil
off sulphur, reducing the sulphides -to a lower stage of sulphurisa-
tion. This sulphur burns in the furnace to sulphur dioxide
(sulphurous anhydride, SO2) part of which coming into contact
with the hot ore and hot walls of the furnace, and the oxidising
furnace gases, is converted into sulphur trioxide (sulphuric
anhydride, SO8). On raising the temperature the decomposition
of zinc sulphate and other metallic sulphates is effected, leaving
oxide of zinc contaminated with the oxides of other metals
present. For the expulsion of the sulphur trioxide from the
zinc sulphate, however, a very high temperature is required,
especially from the basic sulphates, which remain towards the
end of the process, and it is this fact which makes the perfect
roasting of zinc blende difficult.

The oxidation of both the zinc and the sulphur in zinc blende
by atmospheric oxygen during the roasting operation may be
represented by the following equations : —

ZnS + 30 = ZnO + SO2.
2ZnS + 70 = ZnO + ZnSO4 + SO
At a higher temperature, ZnSO4 = ZnO -f SO8.

THE ZINC INDUSTRY

The reactions in blende roasting being exothermic, the ore,
when once sufficiently heated, is self-roasting until the total
sulphur contents are reduced to about 8 per cent. Beyond
this stage the further application of heat becomes necessary in
order to decompose the sulphates, so that the final reactions
are strongly endo thermic, and the temperature of the ore when
roasting is complete is about 900° to 950° C. The amount of
sulphur to be expelled is dependent on the amount of metallic
sulphides associated with the blende. Pure zinc sulphide contains
32-92 per cent, of sulphur, but the ores of commerce are usually
contaminated with iron pyrites (FeS2) and other metallic sulph-
ides and gangue materials, so that the sulphur content is usually
between 21 and 35 per cent.

When roasting has been successfully conducted, the final
product does not contain on the average more than i per cent,
of sulphur. Thus, in the case of certain of the purer ores the
desulphurisation is so complete that no more than 0-5 to 0-8
per cent, total sulphur remains, whilst others equally carefully
dealt with retain from 2 '5 to 3 per cent., and even more in special
cases, particularly those ores containing lime and baryta. Follow-
ing modern Continental practice, however, the sulphur combined
with lime, magnesia, strontia and baryta should be considered
separately from that otherwise present in the roasted ore.

The loss of zinc in roasting is very small and averages only
about O'5 per cent. Probably highly ferruginous blende is the
most difficult ore to roast.

Zinc ores are rarely absolutely free from lead, and the trouble
introduced in the operations of roasting and distillation by the
presence of this metal in substantial amounts prevented to a
large extent the smelting of zinc-lead ores until about 1890,
when they were first smelted on a large scale on the Continent.

Broken Hill ore, containing from 17 to 33 per cent, of lead and
from 28 to 34 per cent, of zinc, was treated in Belgium and
Germany in 1897, the ore being roasted in hand furnaces and the
zinc distilled, after which the residues were treated for the silver
and lead.

Zinc concentrates from the dressing of the Broken Hill ore
were first shipped to the Continent in 1899, and contained from
12 to 15 per cent, of lead and from 38 to 40 per cent, of zinc.
They were first smelted in Belgium and Holland and a little
later in Germany.

THE SMELTING OF ZINC ORES

The treatment of Broken Hill concentrates in this country was
first commenced in 1905 by Mr. H. M. Ridge, who in 1907—1908
built and started the works at Seaton Carew, Durham, where
large quantities of this ore are now treated.

Roasting converts lead sulphide (galena) into lead oxide, and to
lead sulphate, a stable compound very difficult to decompose
even at a high temperature. In the presence of free silica lead
silicate is formed, and since this compound is readily fusible
there is a risk of the ore agglomerating during roasting if it
contains much quartz. Considerable success has attended the
attempts to roast zinc-lead ores, and now excellent desulphurisa-
tion of Broken Hill concentrates, containing about 45 per cent,
of zinc and as much as 10 per cent, or more of lead, is daily
achieved by well-designed muffle roasting furnaces.

It has been found in practice that the rhodonite (mainly
manganese silicate) which is mechanically mixed with the zinc
ore in Broken Hill concentrates has a peculiar beneficent
effect in the roasting, but the reasons for this are not clear,
and the matter requires investigation.

The reactions peculiar to the roasting of Broken Hill concen-
trates appear to reach their maximum effect in muffle roasters,
and are not nearly so noticeable when the roasting is carried out
in furnaces of the "open" type.1 In fact it may be said that
the successful treatment of zinc-lead ores is due largely to the
improvements in the design of modern roasting furnaces of the
muffle type.

The surmounting of the difficulties which at first attended
the roasting and subsequent distilling of the Broken Hill and
similar zinc concentrates is a matter of far-reaching importance,
as it renders available vast additional sources of ore for augment-
ing the world's supply of zinc.

Many types of furnaces are in use for roasting zinc blende ;
they may be classified under four heads, viz. : — •

(r) Hand-raked reverberatory furnaces with one or more
hearths, or with shelf burners.

(2) Mechanically-raked reverberatory furnaces.

(3) Multiple-hearth hand-raked furnaces.

(4) Mechanical multiple-hearth muffle furnaces.

The work of stirring in zinc ore-roasting furnaces is most

1 J. C. Moulden, op. cit., p. 508.

83 G 2

THE ZINC INDUSTRY

laborious, and even on the Continent, where labour is com-
paratively cheap, continuous efforts have been made, since the
beginning of the industry, to replace hand labour by machinery.
The first attempt was made by the Societe de la Vieille Montagne,
who succeeded in carrying out the first part of the operation in a
circular furnace with several hearths, 8 feet in diameter, in which
the ore was stirred by means of rotating rabbles. The ore, after
passing over three or, in some of the furnaces, four hearths,
dropped to two hand-rabbled hearths similar to those used in
the Rhenania furnaces described later. In America, where
hand labour was even more difficult to obtain, it was impossible
to use hand furnaces.

Roasting furnaces of the muffle type are employed when it is
desired to utilise the sulphur dioxide for the manufacture
of sulphuric acid, as the fuel gases never come into direct
contact with the ore, the sulphur gases from which are led by
an independent flue system to the sulphuric acid plant. The
gases that pass to the acid maker contain on an average between
5-5 per cent, and 6-5 per cent, (by volume) of sulphur dioxide.
If below 5 per cent., the acid-chamber reactions are retarded,
while if sensibly above 8 per cent, the roasting is retarded.

Further reference is made to the manufacture of sulphuric
acid from blende roasting on page in.

The utilisation of the sulphur contents of zinc ore has received
considerable attention within recent years on the Continent and
in America, with the result that furnaces of the muffle type,
either hand or mechanically raked, are now largely employed
for roasting blende.

Representative furnaces of this type now in use are (i) the
Hasenclever or Rhenania furnace, (2) the Delplace furnace.
(3) the Hegeler furnace, and (4) the Ridge furnace.

The first two named are hand-worked muffle furnaces and are
almost exclusively used in Europe ; and the third is a mechanical
furnace in general use in the United States. Hasenclever built
his first furnace at the Rhenania Works in Germany in 1855,
and since that time many modifications have been introduced.
In the later modifications, the Rhenania furnace consists of three
superimposed muffles, the fire gases travelling beneath and above
the bottom muffle.

The furnace is 47-5 ft. long and 17-5 ft. wide, so that the ore
travels a distance of 118 ft. along the hearths. With a 12-hour

THE SMELTING OF ZINC ORES

THE ZINC INDUSTRY

THE SMELTING OF ZINC ORES

shift a total of 8 men is required for the production of 6 tons of
roasted ore per 24 hours.1

By working with 8-hour shifts only 12 men were required, and
the production per man per shift slightly decreased.

The coal consumption is about 25 per cent.

These furnaces have been generally built together in blocks
of four and have been more largely used on the Continent than
any other type of furnace.

Owing to the high price of fuel, " Delplace " furnaces have,
since 1895, been largely built in Belgium. Figures I and 2
show the details of this furnace.

The travel of the ore on the seven superimposed hearths in
this furnace is only 40 ft., but the ore is exposed thoroughly to
the air because the arches are low, and only a thin bed of ore is
maintained on each hearth. Only 16 per cent, of coal is required
for heating. It is stated that with good labour, and if carefully
built, these furnaces give satisfactory results. In addition to
those erected in Belgium, some have been built in France, and a
few have been erected in this country and in Germany.

Experienced labour is required to work them satisfactorily,
and the men prefer to work on the Rhenania furnaces, in which
the ore is rabbled sideways, instead of being alternately pushed
from and drawn towards the worker as in the Delplace furnace.

As previously stated, work on zinc ore-roasting furnaces is
most laborious, and continuous efforts have been made to replace
hand labour by machinery, especially in furnaces in which the
gases are used for sulphuric acid production. The mechanical
operation of the muffle furnace, however, presents considerable
difficulty, and although much progress has been made in recent
years, it does not appear to have reached the development and
application which every zinc metallurgist hopes it may do..

The Hegeler furnace, so largely used in America, is a mechani-
cally worked multiple-muffle furnace, in which seven muffles
are placed one above the other, two furnaces being built to form
one block. Figures 3 and 4 illustrate the general design of
the Hegeler furnace.

The three lowest muffles are heated by producer gas, the flame
passing first under and then over them. The ore is rabbled
mechanically by rakes attached to iron rods, so that it travels

1 " The Utilisation of the Sulphur Contents of Zinc Ore," H. M. Ridge,
Journal of the Society of Chemical Industry, 1917, vol; xxxvi, pp. 676-685,

THE ZINC INDUSTRY

from shelf to shelf, finally being discharged through an opening
in the lowest shelf. The rakes are drawn through the furnace
by chains, and after passing through the furnace in one direction
are moved to the level of the next shelf, and then drawn
through this in the opposite direction. This allows of cooling
the stirring mechanism whilst outside the furnace.

These furnaces occupy a very large floor area, and the capital

FIG. 3. — HEGELER ROASTING FURNACE. SECTIONAL ELEVATION.
H=MUFFLES. C = GAS FLUES.

outlay is large. They have been adopted in America on account
of the scarcity and dearness of skilled labour and because coal
is cheap. It is stated that the repair bill of the Hegeler furnaces
working on the Continent is such that there is no appreciable
saving in cost of roasting as compared with hand-rabbled
furnaces. With 8-hour shifts 17 men are required per shift, so

THE SMELTING OF ZINC ORES

that there is no reduction in the
actual number of men as compared
with hand furnaces, but, with the
exception of a few mechanics, the
men can be of the unskilled labour
class.

A 75-ft. furnace roasts 48 tons of
ore to a sulphur content of 1-25 per
cent, in 24 hours, with a consumption
of coal of about 30 per cent, of the
raw ore. The gases from the roasting
contain 4-75 per cent, by volume of
sulphur dioxide and are utilised for
the manufacture of sulphuric acid.

The improvements in the Hegeler
furnace since its introduction about
thirty years ago have been only in
structural features and mechanical
details. Most of the new zinc-
smelting plants in the eastern coal-
fields of the United States are
designed to make sulphuric acid,
and are equipped with mammoth
Hegeler furnaces capable of roasting
about 50 tons of blende per day.

Another muffle furnace operated
mechanically which is being experi-
mented with in Europe, and to a
certain extent in America, is the De
Spirlet furnace, invented by a
Belgian engineer of that name. This
is a multiple-hearth turret furnace,
in which the alternate hearths rotate
and the ore is stirred by means of
special bricks projecting downwards
from the hearth above.

In consequence of there being no
metal parts inside the furnace in
contact with the ore, the fuel con-
sumption is low. The capacity of
the furnace is 3 to 3-5 tons per 24

i \

'•=.

THE ZINC INDUSTRY

hours. Good results are stated to have been obtained, but the
campaign is short, and as soon as one or two of the projecting
bricks which stir the ore wear or break off, the furnace chokes
and has to be cooled.

In this country several Merton roasting furnaces have been in
use in South Wales for some years. This furnace, which is of
the open-hearth reverberatory type, has three superposed hearths
and a special finishing hearth, the ore being stirred by means of
revolving iron rabbles attached to vertical shafts which pass
through the top of the furnace and through all three hearths and
are supported in sockets below the lowest hearth. There are
four sets of rabbles for the main hearths, and one or sometimes
two water-cooled rabbles for the finishing hearth. The motion
of the rabbles gives a circular rabbling to the ore, and produces a
slow forward movement of the ore owing to the paths of the
rabbles slightly overlapping. The hearths are level and com-
municate with one another by short vertical channels. The
crushed ore is fed in at the coolest part of the uppermost
hearth, is gradually drawn by means of the rabbles along each
hearth, and finally discharged through an opening in the finish-
ing hearth into a truck below it. The necessary heat is supplied
by a fire-place at the end of the finishing hearth near the discharge
opening. The furnace in use at one of the Swansea works has
four hearths 10 ft. wide, with four sets of rabbles. The finishing
hearth is 6 feet wider than the others, and has two rabbles
cooled by circulating water in the usual way.1

The latest type of mechanical-rabbled furnace used in this
country for roasting zinc blende is the Ridge furnace illustrated
in Figs. 5 and 6, which appears to be gaining favour.

It consists of three muffles placed one above the other, and is
gas fired, the gas being burned only under the bottom muffle or
hearth, experience having shown that it is not necessary, with
proper design, to pass the fire gases both beneath and then above
the bottom muffle as is frequently done. The general design
of the furnace is shown in the illustrations. The ore is
stirred by means of iron rabbles attached to four vertical iron
shafts passing through all the roasting hearths and made to
revolve by suitable mechanism beneath the furnace. The
shafts are each made in one piece and are water-cooled ; about
15,000 gallons of cooling water are passed through the shafts in

1 Gowland, " Metallurgy of Non-ferrous Metals," London, 1914, p. 29.

%, i

THE ZINC INDUSTRY

24 hours to prevent overheating. The rabbles which stir the
ore are easily and quickly renewed and the part to be replaced
weighs only 5 Ib. The ore is fed continuously to the drying
hearth on top of the furnace and passes over three roasting
hearths and finally to the cooling hearth, where it serves to
preheat the air required for the oxidation. The mechanism
of each furnace is driven by a separate electric motor of from
8 to 10 horse-power. The motor and all the gearing are on a
solid foundation beneath the furnace and fully accessible. The
discharge opening is separated from the gearing by a brick wall
to keep out all dust. The furnace runs noiselessly, the only
sound being the hum of the motor. In this furnace Broken Hill
zinc concentrates are roasted down to 0-75 per cent, total sulphur
with a feed of 12 tons of ore per day of 24 hours and a coal
consumption of 10 per cent. The sulphur fumes leave the furnace
with 6J to 8J per cent, sulphur dioxide and at a temperature
of 380° C. so that they can be used satisfactorily for sulphuric
acid production in the lead chamber process. One man per shift
can attend to the furnace and the producer.

Zinc concentrates with 14 per cent, lead have been satisfactorily
treated, and also concentrates with 17 per cent, iron ; when roast-
ing an ore, high in lead or iron, it is essential that a mechanical
furnace be kept working continuously, because half an hour's
stoppage means that the ore on the hearths sets hard and forms
lumps which have to be broken up. It has been found possible
in this furnace to use the rabbles for breaking up the lumps, and
the gearing can, if necessary, be run alternately backwards and
forwards till the hearths are free.

Reduction and Distillation. — The extraction of the zinc from
the calcined or roasted ore is effected by mixing it with crushed
coal or coke and exposing it to a high temperature in fire-clay
vessels or retorts so as to reduce the zinc oxide. The carbonaceous
matter must be in excess to prevent the formation of carbon
dioxide, which acts as an oxidising agent on zinc vapour, in
which condition the reduced metal is obtained.

The vapour distils off and is condensed to liquid metal in
clay receivers attached to the retorts, and a continuous stream of
carbon monoxide issues from the retorts.

Owing to the chemical and physical characteristics of the
metal, the extraction of zinc from its oxide by distillation is by
no means as simple as the reduction of most other metallic

THE SMELTING OF ZINC ORES

oxides. The reaction between zinc oxide and carbon is highly
endothermic, and cannot therefore take place without external
heat. Whether, and to what extent, zinc oxide is reduced
by carbon monoxide is still a question of much controversy.
The oxide is not sensibly reduced by carbon below a
temperature of 1125° C., and in modern practice the retorts
require to be heated to 1400° C. to effect the reduction.
At this temperature the reduced metal is in the condition of
vapour, and is not only extraordinarily susceptible to ordinary
oxidising influences, such as air and water vapour, but is capable
even of being oxidised by carbon dioxide. In ordinary distilla-
tion practice so small an amount as 0-25 per cent, of carbon
dioxide in the retort is quite inadmissible, hence the great impor-
tance of keeping excess of carbon in the retorts.

Under these conditions the condensation of the zinc vapour
to liquid metal is a matter of considerable difficulty, as it can
only be effected within a limited range of temperature, viz.,
between 415° and 550° C. Below 415° C. it condenses to a powder
called zinc fume or powder, which consists of finely divided
metallic zinc mixed with zinc oxide to the extent of 6 to 10 per
cent. If the temperature is much above 550° C. the vapour is
not condensed at all.

Another difficulty also attends the condensation. If the zinc
vapour is much diluted with other gases, it will not condense to
fluid zinc, but only as zinc fume.

The facility with which zinc oxide is reduced is also affected
by the temperature at which it has been produced in the pre-
liminary roasting of the ore. The oxide obtained by roasting
zinc blende requires a higher temperature for reduction than that
from the calcination of the carbonate. Also, the higher the
temperature at which zinc blende has been roasted, the higher is
the temperature required for the reduction of the resulting
oxide.

According to W. Me A. Johnson,1 pure zinc oxide is reduced by
charcoal at 1022° C., and by soft coke at 1029° C. When,
however, the zinc oxide is roasted at 1100° C., reduction with
soft coke only takes place at 1048° C., and on roasting the zinc
oxide at a temperature of 1300° C., reduction is not effected
until a temperature of 1061° C. is reached. In actual practice

1 American Electrochemical Society, see Electrochemical Industry
Journal, 1904, ii, pp. 185-187.

THE ZINC INDUSTRY

it does not appear to be an invariable rule that the reduction
temperature is dependent on the temperature at which the zinc
oxide has been produced, and further investigation on this point
appears to be necessary.

It is customary among smelters of other metals to speak of
the metallurgy of zinc as behindhand and lacking in the care and
completeness which characterise their own practice. When,
however, the inherent difficulties attached to the art of extracting
zinc, as outlined above, are appraised at their proper value, this
reproach is unmerited. Much as it leaves to be desired, the
modern metallurgy of zinc is not substantially inferior in its
methods and practice to that of the other metals in common use.
The difficult and peculiar conditions attending the reduction
and distillation of zinc render it necessary to adopt special
methods of extraction, since owing to these conditions the metal
cannot be extracted in large quantities in blast or reverberatory
furnaces, as is the common practice with other industrial metals.
In zinc extraction the ore charges, which are necessarily kept
in the condition of coarse powder throughout the operation, are
very poor conductors of heat, and to extract the metal it is
necessary to supply heat energy continually by external heating
of the retorts. This imposes a maximum charge thickness of
about 8 in., a 24 hours' reduction period (from charging to re-
charging), the provision of small-sized retorts of specialised con-
struction, and with only about six weeks' life, and generally the
handling of large bulks of raw material in very small quantities.
Also/ it does not pay to carry the extraction of the zinc below a
certain limit, consequently the residues are dumped when still
carrying several units of zinc. Nevertheless, viewing the present
status of the practice in zinc smelting, one cannot but be
impressed by the high extraction results, the low consumption
of fuel made possible by modern methods of gaseous firing and
the reduction of labour involved in the process.

The methods of distillation now in use may be conveniently
classified into (i) Belgian, (2) Silesian and (3) Rhenish or Belgo-
Silesian. The chief differences in these methods are in the shape,
size and arrangement of the retorts in the furnace.

The retorts in the Belgian process are circular or slightly
elliptical in cross section, about 8 in. in diameter, 4 to 4^ ft.
average length and arranged in the furnace in from two to seven
rows.

THE SMELTING OF ZINC ORES

In the Silesian process there is, as a rule, one row of large,
narrow, muffle-shaped retorts to each furnace, although occasion-
ally two rows are used. On an average the retorts are 5j ft.
long, 2j ft. high and 6 to 8 in. in breadth. The Rhenish process
employs retorts somewhat larger than those used in the Silesian
process ; they are muffle-shaped or elliptical, and arranged in
two or three rows. This type is a combination of the best features
of the Belgian and Silesian types, and is the one now very gener-
ally adopted in erecting new plant. The retorts are about 5 ft.
long, 13 in. high and 6 in. wide. A modern type of Rhenish
retort is shown in Fig. 7.

13 ns
i

5 2 ft *> Cross

Longitudinal Section of Retort. Section.

Retort with Condenser attached.
FIG. 7.— RHENISH RETORT FOR ZINC DISTILLATION. SECTION.

The Belgian and Silesian furnaces formerly in extensive use
are being replaced on the Continent and in England by the
Rhenish type of furnace. The Belgian type of furnace is
however, still in use in the United States, although here
also in the more recently erected plants the furnaces have
been so modified that they may be classified as Rhenish. The
type of retort used in the United States is practically the same
for all plants. The length of the retorts varies from 4 ft. to
4-5 ft. in length, according to the size of the furnace, with a
circular interior of from 7*5 to 8-5 in. in diameter.

To the mouth of each retort is luted a simple fire-clay nozzle
or condenser, in which the zinc accumulates, and again fitted
over the mouth of the condenser is a conical sheet-iron tube or
prolong, which serves to condense and collect the " fume "

THE ZINC INDUSTRY

which passes over along with the zinc during the distillation, and
which is detached by the workmen and returned to the retorts
with a subsequent charge. The condensers vary in form according
to the retort capacity, type of furnace and system of distillation.
They may be plain clay cones, conical-bellied to act as a metal
receptacle, or Q -shaped. They are made of less refractory clay
than the retorts, and are sometimes coated with limewash, to
facilitate the removal of adherent material.

Manufacture of Retorts and Condensers. — The manufacture of
retorts and condensers is always carried out in close proximity
to the smelting works, and forms a most important branch of
the art of zinc extraction, since owing to the nature of the process
of distillation there is a constant destruction of retorts, their
life in modern practice being usually from forty to forty-five
days.

The retorts were formerly made by hand, but in modern practice
they are shaped by means of a hydraulic press capable of making
250 in a nine-hour shift. Machine-made retorts are greatly
superior to those made by hand, as they are denser and on this
account more durable and less permeable by zinc vapour. The
material used for the manufacture of the retorts must be
extremely refractory, and considerable difficulty is frequently
experienced in obtaining clay suitable for the purpose. The raw
clay needs careful weathering and pugging before use. Usually
retorts are made of a mixture composed of burnt clay, or chamotte
and sufficient raw clay to act as an efficient binding agent. In
modern practice, finely-divided coke is often used to replace
part of the chamotte, as it assists in retaining the shape of the
retort under great heat and gives density and impermeability.

A typical retort mixture would consist of l :

Crushed burnt clay (chamotte) . . . . 50 parts.

Raw clay .. .... ... .. 40 ,,

Finely-ground coke .'. ' v. '.'. . . 10 ,,

The retorts are dried very gradually by standing upright in
rows in chambers heated to a moderate temperature, and before
being placed in the distillation furnace they are tempered by
gradually heating in kilns until they attain a full red, in which
condition they are transferred to the furnace and luted in position.
An old zinc retort shows a great alteration of texture, zinc oxide

1 J. C. Moulden, op. cit., p. 510.

THE SMELTING OF ZINC ORES

reacting with the alumina of the clay to form zinc spinel,
ZnO.Al2O3, silica being liberated.

In modern plants, the condensers are moulded by means of
a machine capable of producing from 1,000 to 1,200 per shift
of nine hours. The mixture used consists of crushed old retorts
and raw clay, and after leaving the moulding machine they are
carefully dried and burnt before use.

The question of refractories for use in connection with zinc
furnaces has recently received considerable attention, and the
Ceramic Society has appointed a sub-committee to prepare a
report on the subject.

A modern distillation furnace consists of an arched chamber
containing a large number of retorts arranged nearly horizontally
in two or three superimposed rows, one above another, and
supported only at both ends in order that they may be sur-
rounded by flame. Usually the retorts are arranged in two sets,
back to back, with an intervening space for the gas and air-
ports, the furnace being heated by producer-gas firing. The
substructure of the furnace is usually arranged for preheating
the air, or the air and the producer-gas, by a transference of
heat from the waste gases of the furnace. Formerly reversing
regenerative furnaces on the Siemens system were used, but
in recent years counter-current recuperative furnaces have come
into favour. The laboratory part of a zinc furnace, with retorts,
without condensers attached, is shown in Figs. 8 and 9.

The older zinc furnaces were direct-fired by coal, but all modern
furnaces are gas-fired. This results in economy in labour, fuel
and repairs. The gas producers are built either in, or near, the
furnaces, or in some cases entirely independent of them.

The ordinary life of a zinc furnace is about six years, but some
regenerative furnaces have given good results even after eight
to ten years.1

The zinc furnaces on the Continent hold from 100 to 240
retorts ; the weight charged per retort is, according to its size,
from 35 to 50 kg. of ore, plus 40 per cent, reduction coal, or a
total of 47 to 70 kg., with 17 to 25 kg. of zinc.

The zinc dust produced varies, with the character of furnace

and ore, between 4 and 10 per cent, of the spelter produced. The

loss in metal varies between 10 and 15 per cent, according to the

class of furnace and quality of ore. The durability of the retorts

1 J. Gilbert, Mining Journal (London), 1916, vol. cxiv, p. 496.

97 H

THE ZINC INDUSTRY

varies from thirty to forty-two days or more with three tier
furnaces ; that of the tubes varies between eight and twelve

FIG. 8. — ZINC DISTILLATION FURNACE. CROSS SECTION.

FIG. 9.' — ZINC DISTILLATION FURNACE. FRONT ELEVATION.

days. The cost of retorts of 1,800 mm. length is about 45., and
that of the tubes from $d. to 6d. each.

The German zinc smelters have closely watched the develop-
ments in gaseous firing, and in recent years the furnaces of the

THE SMELTING OF ZINC ORES

regenerative type have been replaced by counter-current or
recuperative furnaces. This development was being carried out
very quickly in Silesia in the last two years before the war in
consequence of the rapid increase in the price of coal, which made
it imperative for the smelters to economise in fuel. By replacing
the regenerative furnaces by counter-current recuperative
furnaces the German smelters reduced their fuel consumption
appreciably and got higher extraction results in the distillation.
The type of furnace which is in most general use in this country
is the reversible regenerative gas-fired, but some of the newer
plants have recuperative furnaces.

In America, natural gas has been extensively used for heating
distillation furnaces, and has become a very important
factor in the economic production of zinc in that country.
The utilisation of these natural gas resources has permitted
of the establishment of zinc distilleries in districts which
otherwise offer no special advantage, the capital required
and the working costs being so lowered thereby as to offset any
disability attaching to transport of ore, clays, reducing material
and finished product.1

The process of distillation is not continuous, but consists
of a well-defined cycle of operations repeated every twenty-four
hours.

The reduction of the zinc oxide in the roasted ore is effected
by mixing it with about 40 per cent, of its weight of reducing
material, in the form of coke, coal or anthracite. This propor-
tion is about 2\ times the quantity of reducing material required
theoretically, but it is necessary in order to maintain a reducing
atmosphere in the retorts, which is of vital importance for the
reasons already stated.

As an example of the method of working, a brief account of
the smelting of Broken Hill concentrates at the Port Pirie works,
New South Wales, may be given.2 The distillation plant com-
prises 10 furnaces of the Rhenish type, having two tiers of retorts,
back to back, with three rows of 24 retorts in each tier, i.e.,
1,440 retorts in all. The retorts are elliptical in cross-section,
and measure 5j ft. in length and 13^ in. in height. The heating
is effected by means of producer-gas, the air required for combus-
tion being pre-heated by a counter-current system. The burners

1 Moulden, he. cit. p. 510.

2 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 65.

99 H 2

THE ZINC INDUSTRY

are of the Bunsen type, 18 in. in diameter, with a gas inlet of
9 in. set in the hearth of the furnace between the two tiers of
retorts. Each row of 24 retorts requires the attention of one
man. The charge consists of about 10,000 Ib. of roasted ore
concentrates, 3,000 Ib. of coke, and 1,500 Ib. of coal. This is
thoroughly mixed on the furnace floor and fed into the retorts
through the condensers.

Usually the top and middle rows of retorts receive this charge,
but the lower row, which does not get so strongly heated as the
others, is charged with coke and material scraped from the
condensers during tapping, consisting of zinc oxide and waste
zinc.

The ends of the condensers are next partly stopped by luting
on to them cast-iron tiles which have an inner lining of fire-clay
and a hole for the passage of the evolved gases. This hole has a
small projecting collar, into which is fitted the small end of a
conical " prolong." These iron prolongs serve to collect the zinc
dust not retained by the condensers. The temperature of the
retorts is slowly raised until it reaches 1325° to 1350° C. The
workman judges of the progress of the operation by the colour
of the flame or vapour which is evolved.

When the distillation is complete, the prolong is removed,
and, on releasing the iron tile, the molten zinc flows out and is
caught in an iron ladle. The condenser is next scraped to
remove all zinc and dross. The residue in the retort is removed
by pulling down counterbalanced sheet iron aprons in front of
the furnace to screen the men from the heat, and raking through
holes. The residues fall out and are deflected by the apron
into trucks below, whence they are sent to the lead blast furnace
for the recovery of the lead and silver they contain.

Damaged retorts are next located, and after these have been
replaced charging is recommenced. The whole series of opera-
tions occupies twenty-four hours. The recovery of zinc as
spelter and zinc dust is stated to amount to about 80 to 85 per
cent, of the quantity present in the ore.

The zinc dust collected amounts to about 12 per cent, of the
total zinc obtained and contains about 92 per cent, of metallic
zinc. This is sometimes returned to the furnace for recovery
as spelter. The spelter contains from 2 to 3 per cent, of lead and
is refined by being melted in a reverberatory furnace.

In modern works large condensers are used and the metal is

100

THE SMELTIN^ g

tapped once only into a mechanical ladle running along the
furnace front, but with the ordinary small condensers the metal
is tapped three or four times during distillation, and hand ladles
are used for conveying the molten metal to the ingot moulds.
The formation of some zinc powder is inseparable from distilla-
tion, but the proportion varies according to the method of working
and may be deliberately controlled by placing common salt or
other haloid salt at the mouth of the retort or even in the con-
denser.

This method has been very successful and is the subject of
a patent by H. W. Webster and J. C. Moulden (British Patent
No. 26788, 1910). In Belgium, salt is added to the charge for
the same purpose. The amount of zinc dust produced varies
in Continental works from 4 to 10 per cent., according to the
class of ore and furnace employed.

The exhausted residues drawn from the retorts in the case
of clean ores are usually thrown away. The composition of
the residues naturally depends on the composition of the ores
treated, and with average ores they may be said to contain
as a rule from 4 to 8 per cent, of zinc. Residues containing
lead and silver constitute an important by-product in zinc
smelting and have been considered on p. 118.

In European practice, the amount of metal extracted by the
distillation process is very generally referred to in terms of the
percentage calculated upon the metal content of the roasted ore,
since the smelter generally buys roasted ore and has no knowledge
of the zinc content of the original sulphide ore.

The extraction of the zinc under modern European methods
is given in broad terms as between 80 and 90 per cent., calculated
on the roasted ore contents.

Thus the loss of zinc during smelting is large in comparison
with the losses sustained in the different metallurgical opera-
tions employed for the production of other industrial metals.
The zinc losses are subject to wide variations, according to the
grade of ore, the impurities present and the care exercised in
working. In the treatment of high grade ore carrying from
45 to 50 per cent, of zinc, as smelted in the best operated plants
in Europe and in America, the loss is between 10 and 15 per cent.

A very sensible proportion of the total amount of zinc extracted
from the ore is derived from the treatment of by-products,
consisting of crusts of metal and oxide chipped off the con-

101

J&DUSTRY

densers, condenser scrapings, oxide and dross from the metal
ladles, all of which are recharged into the retorts.

Refining of Crude Zinc. — When pure ores have been employed,
the zinc obtained by the distillation process is generally sufficiently
pure for industrial purposes, but to ensure uniformity of product
as far as possible it was formerly usual to remelt it in large kettles
and recast it. The metal is poured into open iron moulds so as
to produce slabs or cakes about 17 £ in. by 8 \ in. by 2 \ in., weighing
from 45 to 5° lb., and bearing the name of the smelting
company.

Metal containing impurities such as lead is first submitted to
a refining process known as liquation. This consists in melting
the impure metal in large reverberatory furnaces with sloping
hearths, holding from 20 to 30 tons.

As the slabs melt the metal runs down and collects in the well,
or sump, situated at one end of the furnace bed, where it is
kept molten at as low a temperature as possible.

The bulk of the lead separates by gravity and accumulates
at the bottom of the bath, while the zinc, largely freed from lead,
forms an upper layer from which the metal is ladled and cast
into slabs as it collects.

With the exercise of every care, however, it is seldom that by
this means the amount of lead can, in ordinary practice, be
reduced below 1-4 per cent.

Several methods have been proposed in recent years for elimin-
ating the lead in zinc-lead concentrates during the distillation
process. One of these in use at Irvine, on the Firth of Clyde,
consists in placing a filter of carbon, fire-brick, or other crushed
and porous material in the mouth of the ordinary retort. This
filter retains the lead while the zinc vapour passes through and
is condensed.

Both filters and darns are in use in America and are effective
in reducing the lead and iron content of the zinc, but have no
apparent influence on the cadmium. Their effect is shown in the
figures on p. 103 which give the lead content for different
tappings of zinc.1

Their use has also reduced the iron content of the zinc from
0-07 to 0*02 per cent. Dams, however, have not found favour
in the works, as they tend to reduce the yield of spelter.

1 " Zinc Refining," L. E. Wemple, American Institute of Mining Engi-
neers, 1917.

IO2

THE SMELTING OF ZINC ORES

First draw

Second draw

of zinc.

Lead

per cent.

Condenser without dam

0-58

1-48

Condenser with dam

0-28

0-36

Condenser without filter

0-66

1-28

Condenser with filter

0-14

0-15

Another method, devised by Sulman and Picard, consists in
briquet ting the material with bituminous coal and pitch, and
distilling the briquettes in an ordinary distillation furnace,
when the carbonaceous residue is found to retain most of the
lead in the metallic state, and is suitable for lead smelting. In
this process the filtration of the lead takes place in the pores of
the briquette itself.

The highest grades of zinc have to be produced either by the
distillation of pure ores, by the redistillation of commercial spelter,
or by special methods, such as electrolytic separation. The
redistillation of ordinary spelter is responsible for considerable
quantities of the high-grade zinc on the market. It has been
largely used in America, especially since the outbreak of war,
large graphite retorts being used for the purpose. Redistilla-
tion has also been carried out in electric furnaces in Norway and
Sweden and has been very successful. It seems probable that
the electric furnace will find extended application for this purpose
in the future.

According to Juretzka,1 " electrically heated furnaces are
much more advantageous for the redistillation of zinc than the
ordinary gas-heated muffle furnaces, as the temperature can be
closely adjusted. A central condensing system is more eco-
nomical than muffles fitted with condensers, and enables the
process to be carried out under reduced pressure. High-grade
zinc containing 997 to 99-8 per cent, of zinc is obtained from
refined metal containing lead i-o per cent, and iron 0*03 per
cent, by distillation at low temperatures in electric furnaces.
The yield of pure metal is from 70 to 75 per cent."

1 " Manufacture of Pure Spelter," F. Juretzka, Chem. Zeit., 1916, xl,
pp. 885-886, 894-896. (Abstract, Journal of Society of Chemical Industry,
1916, xxxv, p. 1263.)

103

THE ZINC INDUSTRY

Redistillation is essentially a fractional distillation process,
the more readily volatile zinc being distilled and condensed,
leaving behind the lead and iron in the distillation vessel. When,
however, much lead is present in the crude zinc, the separation
of this metal is never complete by redistillation. The process
still leaves more than 0-25 per cent, of lead in the redistilled metal,
and cadmium when present is also carried over with the zinc.

The electrolytic process, where available, produces a higher grade
of spelter from impure ores than does the distillation process ;
a large portion of these impurities in the ore, which by the
distillation process would be carried into the spelter, is removed
in the leaching of the ore and the purification of the zinc solution.

Recent Advances in Zinc Smelting

Whilst progress has been made in the metallurgy of zinc of
late years, it has not been characterised by any great change
in method, or by the discovery of new principles, but rather by
a continuous and steady improvement in detail, an increase in
the productive capacity of the existing works, and by the installa-
tion of new plants. Nevertheless, the minor changes have been
important, and have been directed mainly towards higher extrac-
tion results and the reduction of labour. Whilst several new
processes of zinc extraction are being experimented with on a
comparatively small scale, these are not yet sufficiently developed
to determine their influence on the future methods of metallur-
gical treatment of zinc ores.

The principal changes in zinc smelting in recent years are
in the method of firing, first by the introduction of gas
producers and reversing regenerative furnaces, and then by the
adoption of counter-current regenerative furnaces, the use
of machine-made retorts, the increase in the size, shape and
dimensions of retort, from the Belgian to the Rhenish type,
the use of improved condensers, large ladles for tapping,
refining the metal without remelting, and mechanical mixing
and transport of materials.

By these means the cost of production has been reduced and
the yield of metal increased.

In the old direct-fired furnaces the coal consumption was over
two tons per ton of ore smelted, whereas in modern gas-fired Bel-
gian furnaces the consumption of coal for fuel is about 1-6 tons per

104

THE SMELTING OF ZINC ORES

ton of ore smelted. For Rhenish gas-fired furnaces the average
has been about i-i to 1-2 tons, but at present it is i ton
of coal per ton of ore ; much necessarily depends, however, on
the quality of the coal. With a view to the reduction of the
cost of labour, mechanical appliances for charging and cleaning
the retorts have been introduced in several European works,
and more recently in American works, but they have not yet
come into general use.

The ore charged into the retorts generally contains about 45 to
50 per cent, of zinc. The weight of the charge varies with the
size of the retorts, the Belgian retorts in the United States taking
about 60 Ib. plus a small quantity of by-products, exclusive of
reduction material, whilst for Rhenish retorts in Europe it is
from 85 to no Ib. Although the Saeger charging machine is
now in regular use at the works of the National Zinc Company
at Bartlesville, Oklahoma,1 where it was introduced in 1913, the
common arrangement of the distillation furnaces in American
works is unfavourable to the use of a charging machine, American
practice being to set the furnaces in parallel, whereas in modern
European practice they are commonly set in series, i.e., in a
single row, thus allowing more room for manipulation. Machine
charging takes one hour, as compared with three hours for hand
charging, and the ore is charged more densely, enabling 2,000 Ib.
more ore to be charged into each furnace.

Two difficulties, however, attend machine charging when
applied to the excessively fine flotation concentrates now coming
to the zinc smelters. This very fine ore sticks to the augers,
necessitating frequent cleaning during charging, and also tends
to " blow out " with considerable force, sometimes only twenty
minutes after they have been charged.

The method of removing the residue from the retorts generally
employed in Europe is to rake them by hand into a pit in front
of the furnace ; in America the common practice appears
to be to use a long iron pipe, with water flowing from the end,
which is pushed to the back of the hot retort, where the water is
converted into steam by the heat, throwing the charge forward.

By this method a considerable amount of fine material is blown
away, causing loss of any silver or lead contained in the residue.

A retort-discharging machine has recently been patented by
J. J. Simmonds, of lola, Kansas, which in the opinion of some
1 " Mineral Industry," 1915.
105

THE ZINC INDUSTRY

distinguished American zinc metallurgists has solved the problem
of mechanically discharging retort residues. It is stated that
the machine has been installed at three zinc-smelting works in
America. It consists essentially of a truck carrying a series
of bars, or plungers, with sprockets at each end of the bar,
over which travels an endless chain of scrapers. The machine
is run up facing a tier of retorts, into which the scrapers are
introduced and set in motion, the mechanical arrangements being
very ingenious. The scraper chains are sprayed with water to
keep them cool.

Careful attention is also given in America to the gangue con-
stituents of the ore and the composition of the ash from the
reducing agent employed, with the view of reducing the amount
of slagging in the retorts. Iron, lime and manganese are the
most objectionable impurities. Few American smelters care to
have more than 2j per cent, of iron present, but in Europe 7
to 8 per cent, is allowed, whilst ore with even as much as 22
per cent, has been successfully smelted.

The utilisation of the unburnt coal in retort residues is another
matter claiming the attention of American zinc smelters.
The residues, which contain a good deal of unburnt coal, are
screened, and all material over J in. in diameter is mixed with
about 20 per cent, of fresh coal and used as fuel under steam
boilers. So far this mixture has proved serviceable at the works
of the Edgar Zinc Company, and ten boilers are now fired in
this way.

In modern German and Belgian practice a 90 to 94 per cent,
yield of spelter is constantly reached with roasted blende carrying
50 per cent, of zinc. In the Western States of America the yield
from a 40 per cent, ore is stated to be about 75 to 80 per cent.,
but in the newest plants efforts have been made to bring the
yield up to that in Continental works.

Before the outbreak of war the English zinc smelters could not
claim equality with the better Continental practice, the yield
in this country in the past having been generally nearer 85 per
cent. Although progress has been made in British works during
the past decade, and gas-fired furnaces have almost completely
replaced the older Welsh-Belgian type, much remains to
be done in the older works to bring British practice up to the
level attained in several Continental centres. During the past
four years, however, there has been a considerable advance in

106

THE SMELTING OF ZINC ORES

the methods of British zinc works, and wherever new plant has
been erected it has been of modern type, and should be productive
of results equal to those obtained on the Continent.

In the past many attempts have been made to use vertical
retorts in the distillation process, with the view of reducing
the labour of charging and discharging the retorts, which is the
principal part of that required in distillation. Hitherto such
attempts have not been successful, mainly owing to the charge
hanging in the retorts and preventing the gases and zinc vapour
from escaping properly. More recently, however, the question of
vertical retorts has been taken up on the Continent, and as the
result of experiment it is now claimed that the old difficulties
have been overcome. The reduction of the charge has been
made a continuous process by the employment of vertical retorts
in the Roitzheim-Remy furnace installed at Hamborn in West-
phalia. In this process, " continuous reduction is obtained by
feeding the preheated charge of ore into the top of a vertical
retort, and discharging the cooled residue mechanically from
the bottom of a cast-iron cooling chamber.

" The retort is open, top and bottom, but is sealed from the
atmosphere by the charge and ashes. The clay condenser is
arranged perpendicularly to the retort in a niche suitably heated,
the front end being connected to a tube leading to the ' prolong '
catching the zinc dust, and the escaping carbon monoxide is
burnt to ascertain if uncondensed zinc is present, the gases being
passed into the main chimney. The furnaces are heated by
gaseous fuel on the regenerative principle, and require little
attention beyond superintendence of the machinery and tapping
of the zinc once in twenty-four hours. Zinc of 98-6 to 99-0 per
cent, purity is obtained, and is fairly free from lead. Several
advantages over the Rhenish smelting system are claimed for
the process, including the reduction, by 40 per cent., of the
labour required, the lessened consumption of refractory materials
in muffles and condensers equal to about 45 per cent., and a
saving in tools, machine work, heating coal and general costs,
but against these economies must be set the greater use of power
for driving the discharging machinery, pumping cooling water,
etc.

"The net result is stated to be, in the production of 15,700 metric
tons, a saving of about £20,000 (407,000 marks).

" There are also the advantages of increased extraction, smaller

107

THE ZINC INDUSTRY

mechanical losses of ore and metal, the furnaces have much less
dead space, are easier to regulate and superintend, and the furnace
room is free from fumes.

"The costs of installation of both systems, without the dis-
charging machinery, are stated to be about the same, though the
wear and tear on the parts of the machinery are so small that their
ultimate cost is negligible." l

In commenting on this process, Mr. W. R. Ingalls,2 a well-
known American authority on zinc smelting, states that it may
be accepted from Hr. Liebig's description, given above, that the
continuous smelting of zinc ore in a vertical retort is an accom-
plished fact, and the development of the Roitzheim-Remy
furnace "should be watched carefully.

In 1916 application was made by the Swansea Vale Spelter
Company for the transfer of German patents relating to the
smelting of zinc ore in vertical retorts, and the employment of
machinery for scraping the lower part of the furnace, with the
object of erecting vertical retorts in this country to test the
feasibility of the process as a commercial method of zinc pro-
duction.

With a view to economise fuel and labour, and to render the
process of zinc production continuous, numerous attempts
have been made to smelt zinc ores in the blast furnace. All
such attempts have failed, however, owing to inability to control
the percentage of carbon dioxide which so readily oxidises zinc
vapour at a red heat.

The small size, confined character and presence of an excess
of carbon in the charge are conditions which in the ordinary
retort process result in the carbon dioxide being kept within
the necessary limits.

In the blast furnace the zinc can be reduced and separated from
the ore as vapour, but owing to the conditions of working the
vaporised zinc, which has to travel by the same outlet as the
waste furnace gases, is much diluted with carbon monoxide and
nitrogen, and is oxidised by the carbon dioxide invariably present,

1 " The Roitzheim-Remy Continuous Zinc Distillation Process," by
M. Liebig, Metall und Erz, 1916, xiii, pp. 143-156 ; also Metallurgical
and Chemical Engineer , New York, 1916, xiv, pp. 625-629. The abstract
quoted is from the Journal of the Society of Chemical Industry, 1916, xxxv,
p. 846.

a Engineering and Mining Journal, New York, 1916, cii, p. 623.

108

THE SMELTING OF ZINC ORES

•

so that only zinc oxide is produced. Apart from the fact that
the condensation of vaporised zinc can only be effected within a
limited range of temperature, it has been found that the zinc can
be oxidised by as little as 0-5 per cent, of carbon dioxide in the
furnace gases or by water vapour.

By rapid cooling of the furnace gases and other methods, it
has been found largely possible to overcome this oxidation, but
so far the process does not appear to have been generally employed
on a commercial scale.1

Attention has already been drawn to the zinciferous dust
which collects in the flues of the blast furnaces in which iron and
manganese ores containing small quantities of zinc have been
smelted. The percentage of zinc in the ores is very small, and
its recovery affords an interesting metallurgical example of how
the treatment of an iron ore, valueless as such from the point of
view of zinc, results in a by-product containing often as much as
75 per cent, of zinc and correspondingly valuable.2 It is produced
by many of the iron blast furnaces in this country and in Sweden,
and in the works at New Jersey, in the United States of America.
It is a most important by-product in smelting franklinite residues
for ferro-manganese.

Blast furnace smelting also implies the production of a fluid
slag that will flow readily from the furnace, a condition pro-
hibiting any excess of carbonaceous material, and one that is
difficult to attain in view of the tendency of zinc to pass into
the slag and render it pasty unless a high temperature is attained.
It has been shown, however, that this difficulty may be overcome.

In ordinary blast furnace practice a temperature of 1400° C.
was once considered high ; but now a temperature of 1500° C.
and upwards is reported. The conditions for low zinc retention
in the residuum are, according to W. R. Ingalls,3 a high tempera-
ture and a highly calcareous slag. Slags of this nature con-
taining less than i per cent, of zinc have been made.

The smelting of complex zinc-lead ores in the blast furnace in
the ordinary way suffers from two main disadvantages ; upon
the one hand the ores contain too much lead for the ordinary
distillation process of zinc extraction, and on the other they
contain too much zinc for lead smelting, their reduction in the

1 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 70.
3 J. C. Moulden, loc. cit. p. 501.
3 Experiments at McGill University, 1912.
109

THE ZINC INDUSTRY

•

blast furnace being hindered by the excess of zinc, which requires
special amounts of flux, and thus is slagged off and lost unless
the slag is specially treated to recover the zinc.

The recovery of zinc from slags containing large quantities
of the metal has been carried out by H. Pape's process at several
places on the Continent, notably at the Oker Smelting Works
in the Lower Harz district, where it has been applied to the
treatment of the various complex ores from the Rammelsberg
deposits, the main varieties of which are lead ores with 9 per
cent, of lead and 20 per cent, of zinc, and copper ores with from
i to 15 per cent, of copper and i to 20 per cent, of zinc. The
ores are first subjected to a sulphurising roast and leached to
remove some of the zinc ; the residual ore is then smelted with
fluxes in the ordinary way in blast furnaces.

The slags, containing from 22 to 27 per cent, of zinc oxide,
are crushed to 50 mesh, mixed with coke screenings, and the
mixture made into briquettes by means of pitch. The briquettes
are then raised to a high temperature in a continuous rever-
beratory furnace, where the zinc after volatilisation as metal is
carried off as oxide by the flue gases. After dilution with cold air,
the gases are passed through bag-house plant to collect the oxide.
The better quality caught in the bags is sold as a pigment, the
rest is sent to a local zinc works, where it is used for enriching
poor zinc ores, in order that they may be treated by the Belgian
process.

Under conditions of forced oxidation, such as in the blast
furnace or blowing hearth, lead is as freely volatilised in the
form of oxide as is zinc, a fact which has been utilised in Germany,
where the blowing of oxidised low grade zinc-lead ores has been
practised, bag-house plant being employed to collect the mixed
oxide fume. This fume is then treated with sulphuric acid for
the production of crystallised zinc sulphate, the residual lead
sulphate being sold to the smelter.

CHAPTER VI
, ZINC SMELTING (continued)
By-products in the Smelting of Zinc
Sulphuric Acid

NOT the least important of the varied problems that present
themselves in the extraction of zinc from its ores is the disposal
of the sulphur dioxide resulting from the roasting of blende.
Not only has this to be considered on the ground of health
and the preservation of vegetation, but there is the further
important economic consideration of utilising the sulphur
gases for the manufacture of sulphuric acid, and thus securing
a valuable product that is not only essential to chemical industry,
but one that also plays an important part in many other
industries.

As previously pointed out, where the manufacture of sulphuric
acid is one of the objectives, certain conditions are imposed
upon the roasting of blende, the most important of which is the
conducting of the operation in muffle furnaces, as the sulphur
fumes must not be contaminated and diluted with fire gases.

Most zinc ores are free from arsenic, consequently the sulphuric
acid made from blende roasting usually commands a higher price
than that made from iron pyrites, which almost invariably
contains arsenic. On the other hand, zinc ores frequently contain
fluorine, as calcium fluoride (fluor spar), which flotation and other
concentrating methods have, unfortunately, not, up to the
present, been able to separate effectively. Calcium fluoride is
decomposed in the roasting furnace in the presence of silica and
forms silicon fluoride, which is subsequently decomposed and
causes the brickwork in the furnace to be appreciably attacked
unless special precautions are adopted.

THE ZINC_ IND USTR Y

When the sulphur dioxide from blende roasting is converted
into strong sulphuric acid of 60° Be*, the yield from i ton of
40 per cent, zinc blende amounts, on the average, to 80 to 90 per
cent. Whilst the old-established English lead chamber method
of sulphuric acid manufacture has to meet the increasing
competition of the newer contact processes, these up to the
present have found but little application in this country in
connection with zinc ore roasting, although contact processes are
in use in America and in Germany.

The lead chamber process, when working with hand-rabbled
roasting furnaces, has to be carefully watched because of the
irregular evolution of sulphur dioxide in consequence of inter-
mittent rabbling of the ore. In Germany it has been usual to
reduce this difficulty by arranging for the furnace hands working
on the different furnaces to start their shifts at different times,
but, in spite of this, it is not possible to obtain a continuous
current of uniform gas throughout the twenty-four hours, and,
unless the process is watched carefully, loss of nitre will result.1

With modern mechanical furnaces this difficulty is completely
overcome. Apart from some increase in the manufacture of
sulphuric acid from blende roasting, there has been a large
increase in the operation of contact plants for sulphuric acid
production in this country since the outbreak of war, both as
regards extension of existing works and the erection of new
ones. Acid production was considerably increased in 1915 and
1916, and further small increase is in prospect. The import-
ance of contact processes is therefore claiming the attention of
British sulphuric acid manufacturers.

The contact process consists essentially in bringing about the
combination of sulphur dioxide and oxygen by contact with
heated finely divided platinum (hence the name " Contact
process ") and hydrating the sulphur trioxide so produced in
the presence of strong sulphuric acid.

Hitherto the recovery of the sulphur from blende roasting
has not received in this country the attention its great importance
demands, and in this respect the British smelters are behind those
on the Continent and in America, who have for some years given
considerable attention to the production of sulphuric acid as a
valuable secondary product of zinc smelting. As recently

1 H. M. Ridge, " The Utilisation of the Sulphur Contents of Zinc Ore,"
Journal of the Society of Chemical Industry, 1917, vol. xxxvi, pp. 676-684.

112

ZINC SMELTING

pointed out by Moulden, it is now the practice in most European
and many American works to carry on the blende roasting in
conjunction with the manufacture of sulphuric acid, and this
for two main reasons : (i) the restriction imposed by legislation
in most thickly populated districts upon the discharge of
sulphurous gases into the atmosphere, and (2) the value of
sulphuric acid in such localities, due to the fact that they are
consumers of the acid, and it therefore pays to utilise the
sulphur.

It is not uncommon in Europe to find the roasting and the
manufacture of sulphuric acid carried on in one district where the
call for the acid is considerable, and the roasted ore distilled in
another where conditions as to fuel, clay and labour are the more
favourable. Economic considerations govern, of course, each
individual case, and this system has reached its greatest
development in Belgium and Germany, largely owing to the
abundant and cheap facilities for transport afforded by the
various canal systems.

SULPHURIC ACID PRODUCTION IN UPPER SILESIA.

Year.

Raw
blende
roasted.

Sulphuric
acid
reduced
to 50° Be.

Sale A

ralue.

Metric
tons.

Total
marks.

Metric ton of
50° B6. acid.

1887
1891

1895
1899
1903
1907
1911
1912

53,882
66,236

84,857
123,602
187,596
421,006
411,352

21,013
32,676
33.229
64,029
104,268
139,840

213,317
254,008

479,000
746,000
778,000
1,074,000
1,728,000
2,187,000
3,025,000

Marks.
22-81
22-85
23-43
l6/77
16-62

15-65
14-18

To illustrate the importance of the utilisation of the sulphur
of zinc ores, Ridge gives the above figures for the output
for Upper Silesia prior to the war. In normal times this
district produces about 60 per cent, of the spelter made in
Germany, but a considerable amount of calamine ore is still

113 i

THE ZINC INDUSTRY

available there, so that the maximum production of sul-
phuric acid from blende has not yet been reached ; the
tonnage of calamine treated is, however, steadily decreasing,
but this is compensated for by an increase in the amount of
blende treated, and permits of an increasing spelter and acid
production. The last figures available are for 1912, and the
table on page 113 shows the results for every fourth year
since 1887.

The rapid annual increase in the production of sulphuric acid
in the Upper Silesia district in recent years is shown by the
following statement. In 1900 the production of sulphuric acid
per ton of crude zinc produced amounted to only 0-08 metric
ton ; in 1905 it had increased tenfold to 0-85 metric ton, and in
1913 it still further increased to 1-34 metric tons.

" Prior to the war six works in Silesia still used their old
reverberatory furnaces, so that not all the sulphur could be
utilised, but for some years factory legislation has prohibited the
emission of noxious fumes, and as the plants become worn out
they have to be replaced by modern installations. The fumes
from the reverberatory furnaces are scrubbed with milk of lime
which is sent to waste. Five plants have lead chambers and
make acid of 50-55° Be. ; this is generally concentrated in
cascades or Kessler apparatus and in recent years largely in
Gaillard towers. Three works have contact plants as well as
lead chambers. There was in 1912 a total of 48 lead chambers.

" Of the total production of acid,

41,055 metric tons was sold as acid of 50° Be.
114,346 metric tons was sold as acid of 5o°-6o° Be.
42,349 metric tons was sold as acid with 98-100 per cent. H2SO4.
216 metric tons was sold as oleum with 20 per cent. SOS,
4,774 metric tons was sold as SO3.,
and in addition 2,855 metric tons of liquid SO2 was made.

" The acid is used for making superphosphates, sulphate of
ammonia, dynamite, and guncotton, and for refining mineral
oil. It is distributed by rail over a wide area, some going into
Russian Poland, Austria-Hungary, and even to Roumania.

" The position in the zinc smelting districts in Western Germany
is analogous, but the make of acid there is larger in proportion
to the production of spelter, because there is no local supply
of calamine. The newer smelting works have been placed on
navigable waterways so that freights on raw materials and
finished products are low. The chamber process is used in all

114

ZINC SMELTING

the works except one, which has a contact plant ; there is also
one installation making liquid sulphur dioxide.

" In 1913 in Germany 554,760 metric tons of blende was
roasted for making sulphuric acid ; of this 87,439 tons was
imported from Australia and 56,181 tons from other countries.

" In Belgium blende is mainly roasted by the chemical manu-
facturers, who retain the sulphur and receive from the zinc
smelter in addition a payment of 6 to 8 francs per 1,000 kilos,
for roasting the ore. This was facilitated by the low freights
on the canals, which reduced transit charges to a very low figure.
In Belgium 65 per cent, of the total production of sulphuric acid
is made from blende ;' the amount of zinc acid is nearly 400,000
tons." x

In America, fourteen zinc smelters make sulphuric acid,
mainly by the contact process. With the movement of the
zinc smelting industry to the eastward, which has taken place
in recent years in America, the separation of blende roasting and
zinc distillation has become more pronounced, as it has been for
a long time in Europe.

It is now regarded as good practice to roast the blende at some
convenient centre for the distribution of the sulphuric acid, and
then to reship the roasted ore to a suitable place for zinc distilla-
tion. This is now being done by many of the larger concerns.

The American production of sulphuric acid from blende,
calculated as 60° Be. acid, in modern times is as follows 2 :

Year.
1911
1912

1913
1914

1915

Production
in short tons

(2,000 lb.).
230,643
292,917
296,218
411,911
484,942

The average price realised in 1915 was 8-85 dollars per short
ton. The use of the contact process for the treatment of the
sulphur fumes from blende has made its biggest strides in the
United States because the smelters are largely able to rely for
their ore supplies upon the produce of one or more home mines,
and are not dependent upon small lots of ore shipped from various
parts of the world, as has been the case in this country and on
the Continent. Consequently, the American smelters have been

1 Ridge. 2 ibid., loc. cit. p. 683.

115 I 2

THE ZINC INDUSTRY

able to make provision for eliminating any harmful ingredients
which may be present in the ore which they expected to be treating
over a long period. The American smelters also have the advan-
tage of having practically no hand-rabbled furnaces, all the
blende roasting being done in the Hegeler furnace.

In the United Kingdom, sulphuric acid has hitherto only
been made from zinc ore roasting in three plants, and it is
estimated by Ridge that their combined output of acid does not
exceed 25,000 tons of 140° Tw. acid a year. This amount
corresponds with a production of about 10,000 tons of virgin
spelter, which is approximately one-third the production of
spelter in this country in 1913. Part of this metal was made
from calamine, but since the available supplies of this ore are
steadily decreasing, it is only a question of a comparatively
short time before the whole of the virgin spelter will have
to be smelted from zinc blende. This country has suffered
badly in the past from the existence of wasteful and harmful
metallurgical processes in certain areas, and especially in
the treatment of zinc ores it has been customary to roast the
sulphide ore in reverberatory furnaces from which the sulphur
fumes cannot be used, so that the sulphur is wasted and the
atmosphere polluted. While it is true that there has been
some increase in recent years in the utilisation of the gases from
blende roasting for the manufacture of sulphuric acid, it is much
to be regretted that the Inspector of Alkali Works has had to
report that considerable extensions of roasting plants for zinc
ores were erected during 1915, and that arrangements had
actually been made for further extensions in 1916, in which
no provision whatever had been made for the recovery of the
sulphur.

It is very desirable that such a procedure should be prohibited
by legislation. That the matter is, however, receiving some
attention is evident from the Inspector's latest report, in which
it is stated that further progress has been made in the utilisa-
tion of the sulphur fumes from blende roasting for producing
sulphuric acid, in spite of difficulties connected with the working
of mechanical roasting furnaces and the scarcity of suitable
labour for working the necessary hand furnaces. In the newest
installations, the mechanical reverberatory Ridge furnaces
have been adopted with satisfactory results.

It is necessary to remember that in 1913 the total consumption

116

ZINC SMELTING

of zinc in this country amounted to no fewer than 224,000 tons,
of which 74 per cent, was imported.

After allowing for the metal produced by the British smelters,
the imported metal was about 166,000 tons of spelter in addition
to zinc in other forms. If, as pointed out by Ridge, this quantity
were all made from blende, the roasting fumes could be used to
produce annually 400,000 tons of 140° Tw. acid. There is no
reason why this should not be done and the corresponding
quantity of brimstone and non-cupreous pyrites, and pyrites
with small copper content, now used for sulphuric acid produc-
tion, displaced. Before the war the cost of making 140° Tw.
acid from zinc ore roast gases in this country was only between
Ss. and 95. per ton, so that the operation is remunerative.
Zinc ore must be heated because spelter is required, and if the
roasting is not done here it will be done elsewhere. Cheap
sulphuric acid has always been an important factor in the
chemical industries, and the resources of the Empire should be
used for its production within the Empire.

Although the main commercial use for the sulphur fumes from
blende roasting is the manufacture of sulphuric acid, they are
also utilised to a limited extent for making sulphites and liquid
sulphur dioxide.

" Aluminium sulphate has been made at Flone in Belgium by
passing the roaster gases into large chambers excavated in the
hill-side and filled with alum shale.1 At Ampsin this method
was also used for making alum with gas from reverberatory
furnaces ; it seems that sulphite is first formed, and this readily
oxidises to sulphate.

" The manufacture of liquid sulphur dioxide was started by
Grillo at Hamborn in Westphalia, because the fumes from the
roasting furnaces were low in sulphur dioxide, and it was, at
that time, considered impossible to utilise them for making
sulphuric acid. The furnace gases pass to a scrubbing tower
sprayed with water, which dissolves the sulphur dioxide, and
the liquor gravitates to a series of pans, which are placed over
the burners, the heat of which is sufficient to drive off the sulphur
dioxide gas, which, after being cooled, is compressed and liquefied
at a pressure of 7 atmos. In Germany two plants are in opera-
tion, viz., one at Hamborn and another at Lipine in Silesia, but,
in this country, the method has not been employed on the
1 Ridge£/oc. cit. p. 682.
117

THE ZINC INDUSTRY

fumes from zinc ore. The demand for liquid SO2 is
limited."

Lead and Silver. — These metals form important by-products
in the smelting of zinc-lead ores, such as the Broken Hill concen-
trates, to which reference has already been made (p. 53).

When the ores contain much lead and silver, practically the
whole of the silver and most of the lead will be found in the
residues, which in this case are of commercial value.

They are usually concentrated, after grinding, by simple
water-concentration in jigs and on tables, and the enriched
material sold to lead smelters. The presence of lead is necessary
in residues containing silver, as it acts as a collecting agent for
the silver, consequently the lead content, as well as the silver,
is taken into account when determining the price to be paid for
the zinc blende. A deficiency of lead reduces the value of the
ore because it causes loss of silver.

Zinc Fume. — This is another important by-product in zinc
smelting, and consists of a mixture of finely divided zinc and
zinc oxide. In America, zinc fume is called " blue powder."
This product has increasing commercial value and its utilisation
is dealt with later (p. 171).

Cadmium. — This metal is also obtained as a by-product.
Cadmium occurs in small quantities, usually less than 0-5 per
cent., in many zinc ores, such as the sulphide and carbonate,
and practically all the cadmium of commerce is obtained from
such ores. The metal is reduced by carbon and carbon monoxide
at a lower temperature than zinc ; consequently, in the process
of extracting zinc from its ores, the cadmium, is obtained in the
first portions of the product of the distillation, partly as metal
and partly as oxide. It collects in the condensers and prolongs
during the first two hours, and the product may contain from
5 to 8 per cent, of cadmium. This is submitted to redistillation
to obtain the metal of commerce. Upper Silesia is the chief
centre of cadmium production ; some is produced in Great
Britain, and a small quantity in the United States. The amount
capable of being produced in Upper Silesia is comparatively
large, but there has never been an important demand for the
metal, and consequently its recovery has been undertaken by
only a few concerns, and in limited quantity, most of the
product from which it might be obtained being permitted to
remain in the spelter. The consumption of the metal is small.

118

ZINC SMELTING

Its chief use is in the preparation of certain " fusible " alloys,
in which advantage is taken of its low melting point. It is
also used to a limited extent in electroplating. The metal
possesses some very useful properties, and its electro deposition
may in the future find a more extended application. Compounds
of cadmium are used in photography and also as pigments.

Owing to the limited demand, the metal is comparatively
high in price, but as it occurs fairly abundantly in nature, this
would doubtless be reduced if the demand increased.

Residues from Retorts. — The exhausted residues drawn from
the retorts are, in the case of clean ores, usually sufficiently free
from zinc to be thrown away. The composition of these
residues naturally depends, of course, on the composition of
the ores, and with average ores they may be said to contain
as a rule from 4 to 8 per cent, of zinc. They contain carbon-
aceous matter in sufficient quantity to permit of profitable utilisa-
tion, and attention has already been drawn to the attempts that
have been made in America to turn them to account.

When the ores contain much lead and silver, practically the
whole of the silver and most of the lead will be found in the
residues, which in this case are of commercial value.

They are usually concentrated after grinding by simple water-
concentration in jigs and on tables, and the enriched material
is sold to lead smelters, who also value them for the iron they
contain, which acts as a flux in smelting.

The carbon content in the lead residues or slack is also a
cheap reduction material.

The Cost of Zinc Production

The combined cost of roasting and distilling zinc ore
necessarily varies in different smelting centres, as such con-
ditions as character of ore, cost of raw materials, labour, fuel,
distance from market, etc., differ with locality. The output,
or works capacity, also has an important bearing on the cost of
the metal produced. Practically two and a half tons of ore give
one ton of spelter.

Pre-war British practice was to roast blende in reverberatory
hand-rabbled furnaces at a cost of 115. to 125. 6d. per ton of ore.

This figure compares very favourably with Continental practice

119

THE ZINC INDUSTRY

in modern mechanical furnaces, as shown by the working costs
given below.

In the larger installations in the Swansea district the pre-war
smelting charge of £2 155. od. to £3 os. od. may be taken as the
inclusive cost, and as covering the roasting of the ore.

The following approximate figures have been given by J.
Gilbert,1 as the average cost of smelting one ton of ore at modern
works on the Continent.

The cost of roasting one ton of blende is :

Superintendence
Rolling, &c.
Roasting furnace work
Coal

Per ton of
unroasted
blende.
s. d.
9
3
. . 4 10

2 Q

Repairs
Sundries

Various contributions
Crushing, &c.

Total cost . . . . . . 10 7

Details. — From 2,300 to 2,500 tons of crude blende produced
2,000 to 2,200 tons of roasted ore. Fuel consumption was 23 to
25 per cent, of furnace coal per ton of roasted blende. The cost
of one ton of coal was 125. on the basis price given below. Loss
of metal in roasting, 0*95 to i-o per cent. Maximum value of
sulphuric acid realised 95. Actual cost of roasting, per ton,
15. yd.

The above figures refer to Rhenish roasting furnaces producing
about 8 to 8-5 tons of roasted blende when working normally.
With crude ore containing from 23 to 25 per cent, of sulphur
and about 0-5 per cent, of lime, and retaining after roasting about
i -i per cent, of sulphur, the yield of sulphuric acid from the
extractable sulphur is from 85 to 92 per cent., normally about
90 per cent.

Cost of distillation of zinc ore at a modern Rhenish works
with a producing capacity of 10,000 to 12,000 tons per
annum :

1 " Costs and Profits of an up-to-date Spelter Works," J. Gilbert, The
Mining Journal, London, 1916, vol. cxiv, pp. 480-481, 496-498. (Very
complete details of costs are given in this article.)

120

ZINC SMELTING

Per ton of

ore treated.

s. d.

Management, office, &c.

9 6

Generators (wages, coal), reductive coal

17 6

Repairs of furnace

Fireproof material, tempering
Zinc stores and sieving of zinc dust

5 o
6

Various contributions to funds, &c.

I 0

Sundries (water, light, &c.)

2 9

General expenses . . . . ..36

Each ton of ore treated : total actual costs . . 40 9

Details. — Ore treated, 2,000 to 3,000 tons per month. Produc-
tion, 1,000 to 1,400 tons of spelter and 100 to 140 tons of zinc
dust monthly. Percentage of zinc contained in the roasted ore,
50 to 51 per cent. Loss in smelting (ore poor in lead), 12 per
cent. Durability of retorts, forty to forty-five days. Coal,
furnace, and tempering, 115 to 120 per cent, on ore weight, at
IQS. 6d. to IQS. yd. per ton delivered at works. Basis price main
coal, 135. <}d. delivered at works. Reduction coal, 40 to 45 per
cent, of weight of ore.

The ordinary life of a zinc furnace is about six years, but some
regenerative furnaces have given good results, even after eight
or ten years.

The costs of repairs vary from £150 to £300.

Considerable discussion has taken place since the outbreak of
war as to the possibility of smelting a large proportion of the
Broken Hill zinc concentrates in the United Kingdom.

Without entering into the many problems involved, the
following estimate for the treatment of the concentrates in
Swansea recently put forward may prove to be of interest;
an allowance, equivalent to one-half of the cost of roasting,
is made in this estimate for the recovery of the sulphur as
sulphuric acid.1

The estimate is based on a recovery of 85 per cent, of the
zinc, 60 per cent, of the lead, and 50 per cent, of the silver from
concentrates containing zinc 47 per cent., lead 8 per cent., and
silver 10-5 oz. per ton. On this basis, the spelter recovered
would be 0-4 ton for each ton of concentrate treated.

1 Quoted in the Bulletin of the Imperial Institute, 1916, vol. xiv,
p. 68, but original source not given.

121

THE ZINC INDUSTRY

Roasting

Furnace labour

Fuel and reducing coal

Retorts and condensers

Repairs

Administration and overhead charges

Cost of concentrates at works

Total

Deduct value of residue less treatment costs .

Net total £6 7

The Conditions of Labour in Zinc Smelting

The work connected with the distillation of zinc is very arduous,
and considerable skill is required in conducting the process,
especially in charging the retorts, an operation which needs
great dexterity.

In the chief zinc-smelting centres the workmen are specially
trained, and in many cases the knowledge required for the more
important parts of the process has been handed on from
father to son through several generations of workers. On the
Continent, special provision has been made to train the men
required so that the output shall not suffer from lack of skilled
workers.

There is a general agreement that the labour conditions in
this country, as compared with the Continent, are detrimental
to output. It is not, however, suggested that this is due to
inferiority of the men individually.

Unquestionably the most difficult part of the problem con-
nected with the development of the British industry is the
training and organisation of the labour required for the smelting
process. Difficult though these are, they should be undertaken
without delay, for America has shown that they can be done,
and done rapidly when necessary.

The system of payment of wages adopted in this country
differs from that in use on the Continent. In the British spelter
works the Datal system is in use, a fixed rate of wage being given
per shift, according to the duties to be performed.

122

ZINC SMELTING

On the Continent the system of giving premiums has been
attended with marked success.

At the great Belgian zinc works of La Vieille Montagne, the
smelters and mill men receive, in addition to a fixed wage, a
premium calculated on the output, and a special premium is
also given for unusual energy. In some cases the firemen receive
a similar premium, based on the time their furnace lasts without
repair. In other cases, the workmen receive a premium when
they obtain from the ores a greater amount of metal than that
which they are calculated to yield. Two-thirds of this premium
is paid periodically with the regular wage. The remaining third
is retained until the end of the year, and it is not paid then unless
the workmen have worked regularly throughout the year.

In some of the German works additional premiums are paid on
the production of zinc dust, of metallic lead recovered from the
distilling furnace, and the life of the retorts.

The tendency of zinc smelters within recent years has been
to substitute, as far as possible, mechanical labour for manual
labour. Especially is this the case in regard to roasting furnaces,
but in the case of the distillation process, although mechanical
charging and discharging appliances have been introduced, they
have only been adopted to a very limited extent. The various
operations connected with the distillation process do not lend
themselves readily to mechanical devices. However, attention
is being given to the possible application of mechanical appliances
to the manipulation of zinc distillation furnaces, and a certain
amount of success has been attained, more particularly on the
Continent and in America.

As previously stated, machine-made retorts have now very
largely replaced those made by hand, thus effecting a considerable
saving in manual labour.

123

CHAPTER VII

OTHER METHODS OF ZINC PRODUCTION

The Electric Smelting of Zinc Ores

WHILST practically the whole of the zinc of commerce is pro-
duced by distillation, great efforts have been made in recent
years, and large sums of money spent, in the endeavour to
simplify, expedite, and cheapen extraction, and in particular to
render the process of zinc production continuous.

It is recognised that the distillation process leaves much to
be desired, because the heat is applied uneconomically, as it
has to pass through the walls of the retorts, and in consequence
these retorts must be relatively small, restricting the output of
metal, and much hand labour is required in treating the ore.

Of all the various newer processes that have been devised and
experimented with for the extraction of zinc from its ores only
two may be said to have approached commercial success, viz. :
(i) electro-thermal methods, or electric smelting, and (2) hydro-
metallurgical methods. In the electro -thermal methods the
distillation is continuous, the reduction and distillation being
effected by heat produced within the reducing vessel or furnace
itself ; and in hydro-metallurgical, or wet methods, the zinc is
first dissolved and then recovered from solution by electrolysis.

Both these methods have been applied to the recovery
of the metal in low grade ores and in ores which cannot be
satisfactorily treated by the usual distillation method. The
electro-thermic production of zinc in the electric furnace
was first attempted, in 1883, by the Brothers Cowles, who
developed the resistance type of furnace originated by Despretz
in 1849, m which a core of carbonaceous material in the charge
itself carries the current in a horizontal direction. In 1901
C. P. G. De Laval erected the first electric furnace for smelting

124

OTHER METHODS OF ZINC PRODUCTION

zinc on a commercial scale, and four years later works were
erected in Sweden to carry out his process. Since that time
a considerable amount of attention has been given to electric
furnaces for smelting zinc ores.

As pointed out by Professor Gowland,1 " the chief drawbacks
that impede the commercial success of the application of the
electric furnace to the smelting of zinc ores are the cost of the
current and of the electrodes, the loss of metal and the difficulty
of obtaining a fair proportion of the zinc as metal and not as
oxide, which has to be re-treated."

In spite of these drawbacks, the electric smelting of zinc ores
has held the attention of metallurgists for a long time, and
during recent years a large amount of work has been done on
the problem of treating, not merely the high grade ores that are
easily distilled in the ordinary retort furnaces, but also the low
grade and complex ores that can hardly be treated at all by
existing methods.

In discussing the electric smelting of zinc ores, Prof. A. Stans-
field 2 considers that the first point to make clear is the great differ-
ence between the old practice and the methods attempted by the
electro-metallurgist. In the usual retort, the charge of roasted
ore and coal is heated gradually for a number of hours, driving
off first the moisture and the hydrocarbons from the coal, then
the carbon dioxide resulting from the reduction of easily reducible
metals such as iron and lead, and finally, when a temperature of
more than 1000° C. has been reached, the zinc vapour itself with
its equivalent of carbon monoxide.

Under these conditions the condensation of the zinc vapour
is satisfactory, and a large proportion of the metal is obtained
in the molten condition. This operation could no doubt be
reproduced in an electric furnace, and would have the advantage
that somewhat larger retorts could be employed ; but the electric
furnace inventor is not content with so moderate an attainment ;
he wishes to change the whole process from the present step by
step method to a continuous smelting operation in which the ore
and reducing carbon shall be fed into the furnace at one point,
the zinc flow out of the condenser, in the molten state, at another
point, the slag be tapped off from a third point, and lead bullion,

1 " Metallurgy of Non-Ferrous Metals," ist. Edit., London. 1914, p. 396-

2 A. Stansfield, " Electric Furnaces as Applied to Non-Ferrous Metal-
lurgy," Journal of the Institute of Metals, 1916, vol. xv, p. 289.

125

THE ZINC INDUSTRY

carrying any gold and silver values, shall flow out at a fourth
opening in the furnace.

The task thus set is by no means easy ; if the ore mixture
goes without preparation into the smelting chamber, the moisture,
hydrocarbons and carbon dioxide will come off in admixture with
the zinc vapour and carbon monoxide, and the zinc will condense
from this mixture mostly in the form of a blue powder. By a
preliminary heating of the ore mixture in a separate chamber
the moisture, hydrocarbons and carbon dioxide can be removed
to a large extent, but it is difficult to effect their complete removal.

Thus it appears that there are considerable difficulties to be
overcome before a successful electric furnace process can be
developed.

One difficulty, inseparable from the ordinary process of zinc
smelting, is the need for an almost perfect roast of the sulphide
ore, as a preparation for the distillation process.

Stansfield considers that the electric furnace process, on the
other hand, holds out the hope that this roasting operation can
be dispensed with, or at least that it need not be nearly so
thorough. This possibility depends on the removal of the
sulphur in the electric furnace in combination with metallic
iron, or more cheaply with calcium supplied in the form of lime.

This latter reaction has been studied by O. W. Brown and
W. F. Oesterle,1 who find that it takes place very completely,
in the electric furnace, according to the equation

ZnS + CaO + C = Zn + CaS + CO.

Early experimental work by W. R. Ingalls at the McGill
University confirmed the opinion that, if electric smelting is to
offer any advantages over distillation in retorts, the process
must be continuous, and all modern furnaces are constructed
on this principle. In many of the electric furnaces now in use
the energy is applied with great ingenuity and high efficiency
is obtained, whilst efforts are made to reduce the electrode
consumption to a minimum.

The reduction in the electric furnace seems to take place more
rapidly than in retort smelting, but the reaction between the
carbon and carbon dioxide does not appear to occur to such an
extent in the former as in the retort. Hence the electric furnace

1 " The Electric Smelting of Zinc," Transactions of the American
Electrochemical Society, 1905, vol. viii, p. 171.

126

OTHER METHODS OF ZINC PRODUCTION

contains an atmosphere comparatively rich in carbon dioxide,
so that a larger amount of fume (blue powder) is formed than
when the retort furnace is employed.

Cote and Pierron, Johnson and others have attempted, with
some success, to solve the carbon dioxide problem by such means
as passing the gases through columns of incandescent carbon.
But while progress has been made, the discovery of how to
avoid oxidation of the zinc deposits, as formed under the
conditions prevailing in electric smelting, is still the problem
which metallurgists have to solve in connection with this method
of zinc smelting.

The continuity of operation in the electric furnace implies
discharging the residue as a slag that will flow, and there has
been a tendency for inventors of electric zinc furnaces to render
the charge fusible, so that fluid slags may be tapped as from
cupolas. This condition, however, prohibits any great excess
of carbonaceous material in the charge, and accounts for the
higher percentage of carbon dioxide frequently found in con-
tinuously operated furnaces.

Among the various types of electric furnace now in use, those
of De Laval, Cote and Pierron, and Johnson may be mentioned.
The first two may be selected as typical, and as involving the
two types of electric furnace ; De Laval employs the electric
arc, and Cote and Pierron slag resistance, as means for converting
electric energy into heat.

The De Laval process, which has been carried out commercially
for some years at Trollhattan and Sarpsborg, in Sweden, develops
heat by means of the arc, current being generated from water
power at prices variously given as from 385. to 505. per electrical
h.p.-year.1 The works are equipped for 18,000 electrical horse-
power and produce over 6,000 tons of refined zinc annually.

The process is conducted in two operations, the first being the
smelting of the roasted ore in an arc furnace for the production
of a coarse metal containing zinc, lead and other metals, and the
second the refining of this coarse metal by distillation in another
arc furnace.

Much of the zinc is obtained as fume or dust.

The furnaces are of the resistance type, with one large vertical
carbon electrode passing through the roof, the other electrode
being a carbon block in the bottom of the furnace. Each furnace

1 Sulman, loc. cit.
127

THE ZINC INDUSTRY

has a capacity of about 3 metric tons and smelts nearly 3 tons
of ore in twenty-four hours.

The complex argentiferous zinc-lead sulphide ore is first roasted
to expel most of the sulphur. The roasted ore containing about
7 per cent, to 8 per cent, sulphur is then mixed with anthracite
or coke and flux and charged through a hopper into a closed
electric " melting " furnace, where most of the zinc and some of
the lead are volatilised, and condense chiefly as crude spelter
high in lead, and partly as blue powder, which has to be re-treated.
The other part of the lead is reduced to metal and is tapped
out with the slag. It contains a considerable proportion of the
silver present in the ore. Some matte (fused sulphides) is
formed, and this and the slag contain some of the lead, zinc and
silver. The crude spelter containing lead passes to the electric
refining furnace, where the zinc is distilled, producing, on con-
densation, spelter of high grade, and a further quantity of zinc
dust, leaving the remainder of the lead and silver as base bullion.
Two melting furnaces supply one refining furnace.

The company owning these Swedish works reported recently
that its smelting operations have not yet proved commer-
cially profitable ; considerable progress has, however, been
made and it is hoped that things will eventually turn out well.
About half the cost of smelting is for electric current, and it is
thus evident that very cheap electric power is essential for the
commercial success of the process.

It would appear that the solution of the difficulties connected
with the condensation of the zinc are to be sought, not in the
condenser proper, but in the character of the gas delivered to it.
The attempt to condense a commercial proportion of the vapour
resulting from the reduction of zinc oxide has so far failed, this
being the crucial point of electric zinc ore smelting.

On the basis of ore alone the consumption of power at Troll-
hattan, according to report, was 2,078 kilowatt-hours per 100 kilo-
grammes of ore, but for every ton of ore smelted about two tons of
zinc powder had to be resmelted.

The smelting of 1,000 kilogrammes of ordinary zinc ore
(25-3o per cent, zinc) is reckoned to require from 900 to 1,000
kilowatt-hours. Each furnace smelts about 2,800 kilogrammes
of ore in twenty-four hours.

The Cote and Pierron process is carried out on a small scale in
France, notably at the Arundy Works in the Pyrenees, which

128

OTHER METHODS OF ZINC PRODUCTION

have been in operation since 1904 ; experimental work with this
process has also been carried on since 1914 at Ugine and Iperre,
in Savoy, and at Quenean in Belgium.

An important feature of the process is the smelting of blende
in the raw state, that is, without previous roasting to remove
sulphur. Whilst simplifying the metallurgy of the process, this
method increases the difficulties of operation of the electric
furnace. The Cote and Pierron process is ba^ed on the fact that
iron replaces lead in lead sulphide at a comparatively low tempera-
ture, and zinc in zinc sulphide when the temperature is increased.
It is claimed that the process effects a complete separation of
the zinc and lead. The furnace is a combined arc and resistance
furnace. It is circular, with sides and bottom lined with
graphite, thus giving a conducting lining ; the roof is a low dome
of fire brick. A carbon electrode, which can be raised or lowered,
passes through an opening in the centre of the roof ; the other
electrode, a cone of graphite, projects from the hearth. The
furnace is charged through the roof, and the lead, slag, and
iron sulphides are tapped through an aperture in the side.
The volatilised zinc passes through an outlet in the upper part
of the furnace to the condenser, which consists of a cylindrical,
shaft-like chamber of fire brick filled with coke or anthracite,
and provided with a taphole at its base for the discharge of the
condensed zinc.

The charge, consisting of a mixture of 200 kilogrammes of ore
with iron turnings, and lime as flux, is introduced into the hot
furnace, and the first reaction of iron on lead sulphide is effected
at a relatively low temperature. The resulting lead is then
tapped. The temperature is now raised and the decom-
position of the zinc sulphide by the iron brought about.
The zinc distils over, and is condensed in the condenser,
the carbon in the upper part of which is kept at a red
heat, to prevent as far as possible the formation of zinc fume.
Finally, the iron sulphide and the slag are run out. At the
Arundy Works a furnace of 350 kilowatts, with alternating-
current at 55 volts, treats one ton of blende (35 per cent, zinc) per
95 to 100 horse-power-days.

It is claimed that not more than 2 per cent, of zinc remains
in the slags.

In America a considerable amount of experimental work has
been done with W. McA. Johnson's electric furnace at Hartford,

129 K

THE ZINC INDUSTRY

Connecticut, and it is stated that arrangements have been made
to erect a loo-ton commercial plant at Keokuk, Iowa, for the
treatment of very complex ores. This is a continuous process
with furnace of the resistance type, in which the charge carries
the current.

The charge is heated to about 900° C. in a continuous pre-
heater before reaching the furnace.1 To prevent the formation of
blue powder, the carbon dioxide formed in the smelting zone is
rendered innocuous by passing the gases from the furnace through
an electrically-heated carbon filter, whereby the carbon dioxide
is converted into harmless monoxide.

This process has been investigated by the Dominion Govern-
ment with a view to its application in British Columbia, but
apparently complete success has not yet been reached.

Another process that is claiming attention is the Snyder process,
which has been applied to the treatment of argentiferous zinc-
lead ores. The ore is roasted to oxide, and fluxes added so that
the mixture will melt at about 1000° C. The molten mixture
is then treated in an electric furnace and results in the reduction
of the metals present. The lead, alloyed with the silver, collects
below the slag, and is tapped off, and the zinc which is oxidised
and volatilised is condensed in brick chambers.

Although electric zinc smelting has now passed beyond the
experimental stage and become a commercial process, it is being
continually investigated by those especially interested in this
method of smelting zinc ores. An expert on zinc production,
J. C. Moulden,2 has recently expressed the opinion that, given
favourable primary conditions and the inevitable improvement
to be brought about by experience, the electrothermic method
of distillation will in the future substantially influence the pro-
duction of zinc.

Hydro-metallurgical Processes of Zinc Production

Since Parnell took up the question of treating complex zinc-
lead ores at Swansea in 1881, many wet methods of zinc extrac-
tion have been suggested and experimented upon, but until quite
recently none have met with commercial success owing to their
inability to produce metallic zinc.

1 Journal of the Royal Society of Arts, 1916, vol. Ixiv, p. 513.
* Ibid.

130

OTHER METHODS OF ZINC PRODUCTION

Unlike most metals, zinc cannot be precipitated from its
solutions by common metals, and if other precipitants are used
and it is obtained as oxide, this must be mixed with carbon and
treated by a distillation process in order to obtain the zinc as
metal. Thus Parnell's process consisted in roasting the ore to
sulphate, leaching with water, evaporating the purified zinc
sulphate solution to a paste and adding powdered zinc blende.
This mixture was then heated to produce zinc oxide, which was
reduced in retorts and distilled. The argentiferous lead residue
left in the vats was sold to lead smelters for the extraction of the
lead and silver.

The difficulty of obtaining the zinc in the metallic state has
been the main reason for the slow development of wet methods
of zinc production. However, where formerly it did not pay to
leach out zinc in the form of sulphate, owing to the limited market
for the salt and the prohibitive cost of converting it into oxide,
the growing demand for white pigments free from lead has made
it possible to avoid the necessity of extracting the zinc as metal
by crystallising the dissolved zinc as sulphate.

Thus, as the result of the increasing demand for zinc sulphate
for the production of " lithopone," to which reference is made on
p. IQ3, the unit of zinc in crystalline sulphate has a con-
siderably higher market value at present than a unit of zinc in
the form of oxide for smelting purposes.

More recently, hydro-metallurgical processes have been devised
in which the zinc after having been obtained in solution, either
as sulphate or chloride, is precipitated in the metallic state by
electrolysis ; but while the difficulties which formerly attended
the precipitation of electrolytic zinc have so far been overcome
as to form the basis of recent methods, the high cost of electric
power has operated against the commercial success of most of
these processes.

Letrange was one of the earliest workers in the production of
zinc by electro-deposition ; in his process the crushed blende was
carefully roasted at a low temperature to produce zinc sulphate,
which was dissolved with dilute sulphuric acid. The solution
was then electrolysed, using an anode of lead (or carbon) and a
cathode of zinc.

Electrolytes of zinc chloride solution are said to be more
economical in electric current than solutions of zinc sulphate,
the electromotive force necessary for the decomposition of the

131 K 2

THE ZINC INDUSTRY

former being less than for the latter. In practice, however, it
has been found to be more satisfactory to extract the zinc as
sulphate than as chloride, and in most of the wet processes now
in use the electrolyte consists of zinc sulphate.

Considerable attention has been given during the past few
years to the electrolytic separation of zinc from its ores, especially
so-called complex ores, and a specially pure zinc is now being
satisfactorily produced by this process.

Compared, however, with smelting, the amount of zinc produced
by electrolytic separation is very small, though the importance
of the latter process is gradually increasing in districts where the
special nature of the ore renders the application of hydro-metal-
lurgical processes on a commercial scale possible. There is,
however, little prospect that wet methods of zinc production
will be sufficiently successful on a commercial scale to enable
them to compete with the distillation processes.

The only commercial processes in the electro-metallurgy of
zinc by direct wet methods appear to be those of Nahnsen, of
Hoepfner, and of Dieffenbach.1

The Nahnsen process has been employed at Lipine, Silesia,
since 1893, the electrolyte used being a solution of the double
sulphate of zinc and magnesium. The Hoepfner process is in
operation at Duisburg, in Germany, and two plants were erected
in 1914 at Kristiania and Balestrand, in Norway, for the treat-
ment of Broken Hill flotation concentrates.

A modification of the method originally devised by Hoepfner
has been employed with considerable success in the United
Kingdom at the works of Messrs. Brunner, Mond and Co., near
Northwich, Cheshire, where considerable quantities of zinc of
high grade are now made and employed for the manufacture of
brass for cartridge cases and other articles requiring a highly
ductile alloy.

The ore is roasted to convert the zinc into oxide, which is
then transformed into zinc chloride by carbon dioxide and a
solution of calcium chloride, waste calcium chloride liquors from
the Solway ammonia-soda process being used for the purpose.
This results in the solution of the zinc as chloride and the pre-
cipitation of calcium carbonate. The zinc solution is purified by
a series of operations analogous to those devised by Hoepfner.

1 Abstract of paper by R. Sylvany, Journal of the Institute of Metals,
1914, vol. xii, p, 318.

132

OTHER METHODS OF ZINC PRODUCTION

The iron and any manganese are precipitated by means of
chloride of lime and calcium carbonate, and the other metals,
copper, lead, etc., by the addition of zinc fume to the clear
solution. The purified solution is electrolysed, using revolving
iron disks as cathodes and carbon anodes enclosed in cloth
diaphragms, a current density of 30 amperes per square foot of
cathode surface being employed. The solution for electrolysis
should contain from 0-08 to 0-12 per cent, of free hydrochloric
acid.

The products of electrolysis are metallic zinc and chlorine,
the latter being subsequently converted into bleaching powder.
The recovery of such a valuable by-product as chlorine from a
waste material is a very important factor in the economic success
of this process at Messrs. Brunner Mond's works. The zinc
produced has a purity of about 99-96 per cent.

The Dieffenbach process is applied to a Westphalian iron
pyrites, containing 8 per cent, of zinc, which is converted
into chloride by roasting with sodium chloride, and extracted
by leaching with water. The residue, which is said to contain
only 0-5 per cent, of zinc, is smelted for iron, whilst the aqueous
solution of zinc chloride is electrolysed in double-compartment
vats, the anode compartments being completely closed. The
liberated chlorine is employed in the manufacture of calcium
hypochlorite.

Since the outbreak of war there has been a very important
development in the electrolytic production of zinc in America,
especially at Anaconda and Trail. The processes being used in
American plants are based on sulphuric acid leaching, and sub-
sequent electrolysis of the zinc solution, using lead anodes.
The largest American plant for electrolytic zinc production is
that of the Anaconda Company, at Great Falls, Butte, which
when complete will produce 35,000 tons of electrolytic zinc
annually.1 The ore is concentrated, chiefly by flotation, and
is then roasted until the sulphur content is 2 or 3 per cent.,
mostly as sulphate.

The temperature must not exceed 732° C., in order to avoid
the formation of zinc ferrite. The roasted residue is leached with
spent electrolyte to which a sufficient quantity of sulphuric acid
has been added. A little manganese dioxide, followed by

1 W. R. Ingalls, Transactions of the American Electrochemical Society,
1916, vol. xxix, p. 347.

133

THE ZINC INDUSTRY

powdered limestone, is added to remove iron, arsenic and anti-
mony. Lead, silver and gold remain in the residue, and the
only impurities in the filtrate are copper and cadmium, which
are precipitated by metallic zinc. Formerly zinc fume was used
to precipitate the cadmium, but difficulties were encountered,
and the plan now adopted consists in running the clear solution
through tube mills containing zinc balls.

After filter-pressing, the solution is electrolysed with lead
anodes and aluminium cathodes. The current density is 20 to
30 amperes per square foot of cathode surface (220 to 330 per
sq. m.), and the current efficiency 93 to 94 per cent. The
cathodes, which are stripped every forty-eight hours, are melted
and cast into ingots. The process is said to be particularly
suitable for the fine concentrates obtained by flotation, which
are troublesome to treat in retorts.

At the Welland plant, Ontario, recently erected by the Weedon
Mining Company, the solution of the zinc and electrolysis of the
solution are performed in the same vat, the cathodes being enclosed
in canvas bags. Other works adopt the arrangements at
Anaconda.

It is proposed to use the method employed by the Anaconda
Copper Company, described above, for the treatment of the
complex zinc-lead sulphide ores which occur in large quantities
in the Mount Read district of Tasmania. In these ores the
metals are found in such an intimate state of fine division
as to render concentration almost impossible. After much ex-
periment, chemical treatment has been found to be the only
feasible and economic method of dealing with such ores, and
after trying several methods of wet extraction it is proposed
to use the Anaconda method as stated. This has been
rendered possible by the electric power scheme of the Tasmanian
Government which has been in operation since May, 1915. The
main water-storage basin is the Great Lake, and the present
output is about 10,000 horse-power, but this can be very con-
siderably increased in the future. The probable consumption
of hydro-electric power in Tasmania in the near future for zinc
ore reduction processes is estimated as 2,500 horse-power.1 The
electrolytic production of zinc is proposed by several companies.

1 " Tasmanian Hydro-electric Power and Chemical Industry," F. H.
Campbell, Proceedings of the Society of Chemical Industry of Victoria,
1916, pp. 419-429-

134

OTHER METHODS OF ZINC PRODUCTION

In the Gillies process, the zinc sulphate is electrolysed between
a rotating cylindrical zinc sheet as cathode and lead anodes, with
a woollen diaphragm for separating the gases.

The bisulphate process is another wet method of zinc extrac-
tion which has been tried in several localities, including Tasmania,
for the treatment of complex sulphide ores containing zinc.
In this process the roasted ore is pulped with water and
sulphur dioxide gas passed through the mass, resulting in the
zinc passing into solution as the soluble bisulphite, ZnH2(SO8)2.1
This solution is pumped into another tank where the mono-
sulphite of zinc is precipitated, and this yields the oxide on roasting
in a muffle furnace.

The sulphur dioxide evolved at two stages in the above process
is added to the roaster gases, which are in turn employed as
the source of the sulphur dioxide used in the initial leaching
process. A certain quantity of sulphate of zinc collects in the
leaching solution, and this is periodically recovered by crystallisa-
tion.

The " French " process of zinc recovery, which is in operation
at Silverton, British Columbia, has several points of interest.
Roasted zinc blende is treated with a solution of sodium bisulphate
(nitre cake) containing a small quantity of a manganese com-
pound, usually manganese sulphate. After about an hour the
solution has extracted almost the whole of the zinc, whilst the
iron, lead and silver remain in the insoluble sludge.

The liquor from the first extraction is run on to a second
charge of ore in order to neutralise its acidity, and when this has
taken place the clear solution is run into vats and the zinc re-
covered elect rolytically, using lead and zinc electrodes. Any
manganese present is deposited on the lead as manganese dioxide,
which is redissolved and used over again, whilst the zinc is
deposited on the zinc electrode. As the zinc is electrolytically
deposited, the sodium bisulphate is regenerated, and when all
the zinc has been removed the solution is again ready for use
and is employed in re-treating the charge of ore previously used
to complete the neutralisation of the solution. It is stated that
the process can be employed equally well for low or high grade
ore, although in the former case the cost of treatment is somewhat
higher.

In the opinion of W. R. Ingalls,2 the electrolytic refining of

1 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 69. 2 Loc. cit.

135

THE ZINC INDUSTRY

zinc is only practicable where power is very cheap, or where other
conditions are exceptionally favourable, such as a readily soluble
ore, as at Anaconda, or one high in silver.

The crude zinc ore at Anaconda lends itself very successfully
to treatment by the flotation process, which gives a high-grade
concentrate. This is of such a nature that by roasting and
leaching with weak sulphuric acid the percentage of zinc extracted
as sulphate is unusually high.

This is not often the case with ordinary ores, which very
frequently contain sensible quantities of iron and manganese
which form troublesome compounds in roasting and lower the
percentage of zinc recoverable by lixiviation.

The recovery of silver from zinc ores, which is only 65 per cent,
in the distillation process, amounts to 90 or even 95 per cent, in
the electrolytic process.

The concentrated ore at Anaconda contains 20 oz. of silver
per ton.

The zinc produced is of high purity, and in view of the increasing
demand for pure metal for alloying purposes the electrolytic
methods of zinc extraction are receiving renewed attention,
especially in connection with the recovery of the metal from
by-products and residues, etc., containing zinc. The prospects
of electrolytic zinc in relation to distillation methods of zinc
extraction have been very ably dealt with by W. R. Ingalls
in a recent paper on " Electrolytic Zinc," l to which all interested
in the subject are referred.

1 W. R. Ingalls, " Electrolytic Zinc," Engineering and Mining Journal
(New York), March 4th, 1916, vol. ci, pp. 425-428.

136

CHAPTER VIII

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

ZINC is a bluish- white metal possessing a bright metallic lustre
and is capable of taking a high polish. As usually met with in
commerce and used, the metal is impure, and seldom contains
more than 99 per cent, of zinc. Zinc in a chemically pure con-
dition may be prepared by the electrolysis of a chemically pure
solution of the sulphate or chloride, and if effected with scrupulous
care in every particular will afford zinc of 99-998 per cent, purity.
The pure metal is comparatively soft, being softer than copper,
but harder than tin and silver.

The hardness of cast zinc measured by Brinell's method is
38'!, compared with copper 40-0, and silver 24-8.

Pure zinc is appreciably hardened by quenching in water after
casting. The pure metal is malleable and may be rolled into
thin sheets at the ordinary temperature, but commercial cast
zinc is moderately hard and brittle at the ordinary temperature,
a flat ingot, or cake, of the metal being fairly easily broken across
under a blow from a heavy hammer. Although commercial
zinc is very much less brittle than antimony or bismuth, the
crystalline structure of the metal causes it to split and break
up if hammered or rolled cold. The fracture exhibits large
crystal faces of high metallic lustre, especially when the metal is
free from iron. The appearance of the fracture is characteristic
and affords an indication of the purity of the metal. The fracture
is more largely crystalline the higher the temperature of casting
is above the melting point of the metal. When bent, the cast
metal emits a sound resembling the " cry of tin," but somewhat
more feeble.

The commercial metal becomes malleable and ductile if heated

137

THE ZINC INDUSTRY

to a temperature of from 100° C. to 150° C., after which treatment
it retains its malleability when cold sufficiently to admit of being
rolled into thin sheet or drawn into wire. On a large scale,
however, the metal is rolled hot. At a temperature above
205° C. zinc again becomes so brittle that it may be pulverised
in an iron mortar. In common with other metals, zinc is
hardened by mechanical treatment, such as rolling, and requires
annealing at a low temperature to restore its malleability. It
has been shown by T. K. Rose 1 that, in the case of pure sheet
zinc 1*25 millimetres thick, softening is nearly completed in about
half an hour at a temperature of 125° C.

Zinc is less tenacious than most metals in common use, its
tenacity, according to Karmarsch, being 2,809 Ib. per square inch
when cast, and between 18,703 Ib. and 22,188 Ib. when in sheets
or wire.

Measurements of the tensile strength of rolled zinc have been
made by H. F. Moore,2 which show that zinc, either in the cast
or rolled state, has no definite yielding point. The breaking load
of thin rolled zinc (not more than 0*05 inch thick) was found by
Moore to be about 24,000 Ib. per square inch, and its tensional
modulus of elasticity 11,500,000 Ib. per square inch. Rolled
zinc is somewhat stronger in tension across than with the grain.
The stress developed in punching or shearing the rolled plates is
about 40 per cent, of that developed with mild steel plates.

The sheets are more ductile with the grain than across it.
Results obtained by T. K. Rose3 show that zinc hardened by
rolling is in an unstable condition at the ordinary temperature
and undergoes a gradual change to the soft state. Thus the
scleroscope hardness of rolled zinc was found to be 36, and after
ninety-seven days the hardness had fallen to 31*0. Zinc may
be granulated by pouring the molten metal into water. In hot
water it is obtained in the form of small globules, known as
bean-shot, and in cold water flakes are produced, known as
feathered-shot metal. Both these forms of granulated zinc are
prepared commercially.

The density, or specific gravity, of cast zinc ranges from
6-9 to 7*2, according to the temperature at which it has been

1 Journal of the Institute of Metals, 1912, vol. viii, p. 114.

2 University of Illinois Bulletin, 1911, vol. ix, No. 9. (Abstract Journal
of the Institute of Metals, 1915, No. 2, vol. xiv, p. 230.)

3 Journal of the Institute of Metals, 1912, No. 2, vol. viii, pp. 86-114.

138

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

cast and the manner in which it has been cooled. By rolling the
metal its specific gravity is increased to about 7-25.

The electrical conductivity of zinc is 25*6 to 29*9, according to
the determinations of several observers, and its thermal conduc-
tivity 28-1, compared in both cases with silver as 100.

The atomic weight of zinc is 65*37 (taking O = 16), and its
symbol is Zn.

Zinc melts at a comparatively low temperature, its melting
point being 419° C. ; it boils at 950° C., the vapour burning
in air with a characteristic brilliant bluish-green flame, and
the production of zinc oxide, a soft, white, flocculent substance
resembling wool, and formerly known as philosopher's wool, or
" flowers of zinc." According to Ingalls, zinc burns in the air
at a temperature as low as 500° C. It can be distilled in quantity
at a bright red heat, and on cooling condenses in globules which
coalesce, when a reducing atmosphere is maintained.

When it passes from the cold solid to the molten condition
zinc increases in volume n-i per cent. It contracts but slightly
on cooling from the molten state, and is thus well adapted for
castings. The molten metal retains a small quantity of zinc
oxide, which separates on solidification, presenting very thick
crystal boundaries when examined under the microscope.

Zinc expands T3^th of its length by heating from o° C. to 100° C.

The metal is not affected by pure dry air or by oxygen at the
ordinary temperature, but under ordinary moist atmospheric
conditions it gradually acquires a coating of the greyish-white
basic carbonate which protects the metal from further corrosion.
In consequence of this property, zinc is used in the form of sheets
for roofing purposes, and is also employed as a protective covering
for iron, which when thus coated is said to be galvanised, a term
that is somewhat misleading, since the iron is not ordinarily
coated by electrical deposition, but by dipping the iron into a
bath of molten zinc. The industrial value of zinc is largely due
to this protective property.

Pure zinc is scarcely acted upon by pure sulphuric or hydro-
chloric acid, either dilute or strong. The presence of small
quantities of impurities, however, determines the rate of solu-
tion of the metal, hence ordinary commercial zinc is readily
attacked by these acids with rapid evolution of hydrogen, and
on this account the metal is used as the positive element in
el ect ricjoa.it eries .

139

THE ZINC INDUSTRY

When zinc is brought into contact with mercury, zinc amalgams
are formed which are only very slowly acted upon by dilute
sulphuric acid ; therefore, by the superficial amalgamation of
the zinc plates used for electric batteries, the same result is
obtained as though the zinc were perfectly pure, and no solution
of zinc takes place until the electric circuit is closed. Amalga-
mation protects zinc from corrosion by acids, because the
discharge potential of hydrogen on mercury exceeds the
potential of zinc.

Sulphuric acid dissolves zinc appreciably more slowly than
hydrochloric acid with an equal concentration of hydrogen ions.

Owing to the differences in the crystalline structure of the
metal, cast zinc is less easily acted upon than rolled zinc by dilute
acids. The dark grey residue obtained on treating the com-
mercial metal with acids consists chiefly of lead.

Both pure and commercial zinc are dissolved readily by alkalis.

Water has no action on zinc at the ordinary temperature, if
air is excluded, but at a red heat the metal readily decomposes
the vapour of water and is converted into oxide.

Carbon dioxide very readily oxidises zinc vapour with the
production of carbon monoxide and zinc oxide. This reaction,
as previously pointed out, is of considerable importance as it
constitutes a decisive factor in the metallurgy of zinc, and confines
within very narrow limits the methods that are applicable, on
a commercial scale, to the extraction of the metal from its ores.

Zinc is strongly electro-positive and readily precipitates most
other metals from their solutions. In this connection it finds
industrial application ; e.g. it is in- extensive use for precipitating
gold from cyanide solutions in the cyanide process of gold extrac-
tion.

Zinc unites with most of the common metals to form a number
of useful alloys, the most important of which are the various forms
of brass. The zinc alloys, and also a number of zinc compounds,
of value in the industries, are discussed under the " Industrial
Applications of Zinc " (see p. 161).

The Micro-structure of Zinc

The evidence afforded by the microscope, in relation to the
constitution of metals and alloys, has been of such value that
the systematic study of the micro-structure of commercial

140

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

samples of zinc and its alloys is now very generally undertaken.
In particular, the systematic study of brass and of nickel silver
as revealed by the microscope has claimed a considerable amount
of attention in recent years.

The rapid growth of this new science of metallography,
and the attention paid to it by both manufacturers and users
of metals, is a cause for much satisfaction, as it evidently
indicates that those connected with the British metal industries
are beginning to recognise the fact that any advance in purely
scientific knowledge of metals is capable of being turned to
practical advantage.

The chief points ascertainable by the use of the microscope
are the crystalline state of the metal or alloy, and changes in
the general structure due to varying mechanical or heat treat-
ment, and the constitution of the material, that is to say, the
differentiation of the various constituents which enter into the
composition of the alloys. This is one of the most important
points connected with the modern study of alloys, and much
valuable information has now been obtained by this method of
investigation.

As regards crystalline structure, attention may be directed
to the distinction between the grains of which a mass of metal
is usually composed and the crystallites which compose each
grain, the latter constituting the true crystalline structure. In
each grain the crystallites are arranged in a definite direction or
orientation. When, therefore, the surface of any pure metal,
after having been carefully polished, is lightly etched with a
weak acid or other reagent and examined under the microscope,
it is seen to be composed of a number of separate grains, irregular
in size and shape. If the etching be made deeper it is found that
the grains, besides differing in size, differ also in texture, reflecting
at different angles light thrown upon them.

Examination of the strongly etched surface under a higher
power shows that this difference in texture is due to a number of
small facets in each grain. The facets are oriented, but in any
one grain they are similarly oriented, so that the general surface
of the grain reflects light in a particular direction. Each of
these grains has the uniformity of internal structure character-
istic of a crystal and is, in fact, a crystal. With this fundamental
fact established, the cause of the behaviour of metals under
different conditions, under strain, for example, can be explained,

141

THE ZINC INDUSTRY

but much remains yet to be investigated. In particular, no
completely satisfactory explanation of the manner in which the
individual crystalline grains are cemented together has yet been
obtained.

Well-defined or idiomorphic crystals are seldom found in the
structure of cast metals, while crystallites or the incipient forms
of crystals are predominant. On annealing, however, this
crystallitic structure is replaced by a well-defined crystalline
structure.

Various etching reagents are in use for developing the structure
of zinc and its alloys. For etching the surface of zinc Timofeef l
recommends a mixture of 94 per cent, nitric acid and 6 per cent,
chromic acid, a few drops of this mixture being added to
50 or 100 cubic centimetres of water before use. This reagent
is also recommended by Desch, and has been found satisfac-
tory in practice.

Iodine is found by Gulliver to be most suitable for alloys rich
in zinc or cadmium.2 He uses a solution of I part iodine and
3 parts potassium iodide in 10 parts of water.

Caustic potash and caustic soda are used for zinc and aluminium
and alloys rich in these metals. When caustic soda is used for
etching alloys of aluminium with zinc, a black deposit is often left
on the etched surface. This can be very satisfactorily removed
by dipping the specimen in a solution of chromic acid in water.

The strength of the caustic soda reagent varies from 5 to
20 per cent. A 10 per cent, solution of chromic acid etches zinc,
cadmium and many alloys of these metals, whilst a highly con-
centrated solution of chromic acid is, according to Czochralski, 3
suitable for developing the internal crystalline structure of zinc.

The micro-structure of pure cast zinc consists of comparatively
large grains, often showing a cross-hatching upon their surfaces,
presenting a structure analogous to that of martensitic steel.
A photomicrograph of cast zinc, etched with very dilute nitric
acid, and magnified 100 diameters, is shown in Plate I.4 Another

1 " Revue de M6tallurgie," 1914, No. I, p. 127.

2 O. F. Hudson, "Etching Reagents," Journal of the Institute of Metals,
1915, No. i, vol. xiii, p. 193.

3 " Stahl und Eisen," 1915, vol. xxv, pp. 1073, 1129. Abstract Journal
of the Institute of Metals, 1916, No. 2, vol. xvi, p. 245.

4 Photomicrographs taken for the author by Dr. F. C. Thompson,
University of Sheffield.

142

Photomicrograph of cast zinc
Magnified 100 diameters.

Photomicrograph of cast zinc (showing twinning).
Magnified 100 diameters

PLATE i.

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

photomicrograph of the same metal, treated as before, is also shown
in Plate I . In this latter case the structure consists of allotrio-
morphic crystals with twinning, which is of somewhat rare
occurrence in metals in the cast state.

When the zinc is contaminated with zinc oxide, which is
usually the case with commercial samples, the oxide tends to
separate at the crystal boundaries, giving rise to very thick
boundary lines.

The changes in structure of hard worked zinc on annealing
are discussed by G. Timofeef. Cast specimens of zinc were
prepared and strained in compression. The micro-structure of
zinc crushed in a vice becomes homogeneous, no crystals being
visible under very high magnifications. The hardness increases
considerably. Recrystallisation takes place, however, very
readily on annealing the metal, a very slight rise in tempera-
ture effecting a noticeable change in the micro-structure of the
strained metal. The etching of the samples was effected with
Timofeef's reagent given above. The strained specimens were
annealed at different temperatures ranging from 65° C. to
360° C.

The photomicrographs showed that the average size of the
crystal grain in the annealed specimens increases uniformly
with the annealing temperature, the hardness suffering a corre-
sponding decrease in value, until it finally reaches the same
figure as that found for the cast metal. It was found in all
cases that the size of the grains was greater at the edges than
in the middle of the specimens ; this is ascribed to the greater
amount of plastic strain at the edges of the specimens during
deformation by compression.

It is concluded that the velocity of recrystallisation depends
both upon the temperature of annealing and upon the severity
of plastic strain ; the final size of the crystalline grains when
annealing at a given temperature is limited by the duration of
heating. Under slight shock the large individual crystals
composing cast zinc became striated, this effect being produced
even by removing the ingots from moulds, if special care is not
taken.

The micro-structure of zinc containing lead indicates that at
the freezing point of zinc the still molten lead is rejected and
forms minute globules occupying often the cleavage cracks
caused by the contraction of the crystalline zinc during solidifica-

143

THE ZINC INDUSTRY

tion. This separation of lead is well shown in Plate 2, which in
the lead appears as isolated dots within the zinc crystals. The
cast zinc contained about 3 per cent, of lead, and the structure
was developed by etching with very dilute hydrochloric acid
with the addition of a few drops of a solution of zinc chloride.
The magnification is 100 diameters.

Iron is a frequent constituent of commercial zinc, and when
present above o-i per cent, it forms distinct crystallites which
are readily discernible under the microscope, and, as already
stated, are doubtless the cause of the light specks on the crystal
faces of fractured spelter. Hard zinc, containing about 10 per
cent, of iron, presents a characteristic structure in which the
crystals are well defined even at a low magnification of about 30
diameters.

The microscope affords a very ready means of controlling the
annealing process for brass and other zinc alloys, and has been
adopted for that purpose in several large works. After every
stage of the process samples are taken, rapidly polished, etched
and examined under the microscope. From the size of the
crystals it is easy to determine whether the alloy has been in-
sufficiently, correctly, or over annealed.

The accompanying photomicrographs of brass, containing
60 per cent, of copper and 40 per cent, of zinc, are given as
illustrations of the study of the constitution of brasses by means
of the microscope.

Plate 3 represents the brass (copper 70, zinc 30) as cast,
while Plate 4 shows the appearance of the metal after annealing
for one hour at 750° C. The magnification in each case is 80
diameters.

The etching-agent was a 10 per cent, solution of ammonium
persulphate.

For further examples of the micro-structure of brass and other
alloys containing zinc reference must be made to the researches
on the subject that have been published in the Proceedings
of the scientific societies, notably in the Journal of the Institute of
Metals, and several of which have been mentioned in the Biblio-
graphy appended.

144

Photomicrograph of cast zinc with 3 % of lead.
Magnified 100 diameters.

PLATE 2.

Brass (70 % copper, 30 % zinc) as cast ; showing cored

structure. Magnified 80 diameters. Etched with

10 % solution of ammonium persulphate.

Photomicrograph by Dr. F. C. Thompson,
University of Sheffield.

PLATE 3.

Brass (70 % copper, 30 % zinc) after annealing for

one hour at 750° C. ; showing crystalline structure.

Magnified 80 diameters. Etched with 10 % solution of

ammonium persulphate.

Photomicrograph by Dr. F. C. Thompson,
University of Sheffield.

PLATE

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

Impurities in Commercial Zinc

Owing to the fact that zinc possesses so powerful an alloying
affinity for other metals, and even metalloids, e.g., arsenic, the
commercial metal produced by distillation is invariably con-
taminated with impurities, the amount of which varies according
to the composition of the ore from which the spelter is produced.

The most frequent impurities in spelter are lead, iron, cadmium
and arsenic. From the table of typical analyses given on p. 149
it will be seen that the chief impurities to be guarded against are
lead and iron.

The variations in the lead and iron content in different brands
of spelter examined by R. T. Rolfe x during the years 1913-1916
were as follows :

Brand of Spelter.

Lead per cent.

Iron per cent.

Crown

1-52

0-08

De Boom

0-31

trace

Nouvelle Montagne

0-94 0-03

Revil

0-46-1-73

0-07-0-19

S.S

0-32-3-43

trace

Ste. de Boom

1-65— 2-03

trace

Vieille Montagne

1-47-1-49

0-04-0-07

Vivian & Co.

•

0-83-1-32

0-08-0-12

Lead. — The lead does not usually exceed 2 per cent., although
some spelters are placed on the market containing as much as
3 per cent. It is usual, however, to refine such impure metal
before marketing, since, as already stated, the quantity of lead
present very largely determines the market value of the spelter.

In spelter intended for rolling, a small percentage of lead is
desirable, and up to I-Q per cent, it has no injurious effects on
the malleability or ductility of the metal.

When, however, the spelter has to be used for making brass
which has to undergo severe mechanical treatment, as, for
example, the manufacture of cartridge cases, the presence of
lead exceeding o-i per cent, is very undesirable, the metal being
often somewhat brittle and liable to crack. When present in
quantities greater than 07 per cent., lead tends to produce
bad cracking in spelter castings.

1 Journal of the Institute of Metals, 1916, vol. xvi, p. 201.
145 L

THE ZINC INDUSTRY

Any cheap and readily applicable method for the elimination
of lead from spelter, short of redistillation, would, in the opinion
of Moulden, find both world-wide application and substantial
remuneration.

Iron. — Iron is a very frequent impurity, the amount passing
into the spelter depending more on the method of smelting than
on the ore employed.

When over o-i per cent., its presence is indicated by the grey
appearance, and by the presence of a number of black specks
(crystallites) on the crystal faces of the fractured spelter, while
the pure metal exhibits clear, brilliant crystal faces on fracture.

The zinc may be freed from this impurity by redistillation,
the use of iron tools and appliances being avoided. The effects
of iron are to increase the hardness and brittleness of zinc and
reduce its malleability, but when the refining by liquation has
been properly conducted there is insufficient present to affect
these properties.

For spelter intended for the manufacture of brass 0-05 per
cent, of iron is often specified as the limit, but less than this
amount is preferable for brass of high ductility and malleability.

Cadmium.— Cadmium, being more volatile than zinc, is more
difficult to condense, and is rarely present in spelter in injurious
proportions.

Spelter may, however, contain as much as 2-0 per cent, of
cadmium, but usually the quantity is under 0-2 per cent. Spelter
free from cadmium can only be obtained by single smelting when
the ore is free from cadmium, but by redistilling common spelter
with proper control of the temperature, and separating the first
distillate, a high-grade spelter, low in cadmium, is easily produced.

Cadmium has a pronounced hardening effect on spelter and
tends to increase its brittleness, but its effect on zinc to be used
for the production of alloys requires further investigation. As
the result of practical experience many metallurgists consider
that cadmium up to 0-5 per cent, has no injurious effect on zinc
used in the manufacture of cartridge brass, nickel silver, and similar
alloys.

The specification of military engineers for high-grade spelter
for the production of cartridge brass permits a maximum of
only O'i5 per cent, of cadmium.

Season cracking in brass, which was formerly attributed solely
to cadmium, is now recognised to be the result of internal strains

146

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC

due to improper heat treatment or the entire lack of heat treat-
ment. On the other hand, cadmium if present beyond 0-5 per
cent, is considered to be injurious when the spelter is used for
sheet rolling, for galvanising, and for making slush (ornamental)
castings. Its presence in galvanising is very important, as
brittleness due to cadmium causes the coating to peel off. This
is of particular importance in galvanised wires for telephone and
telegraph purposes, which are sharply bent in making splices.

Cadmium has a strong tendency to make castings crack. In
brass cadmium tends to act like lead, and is also said to make the
metal more sensitive to heat treatment. The amount present
in brass is, however, seldom large, since it *readily volatilises
during melting.

Arsenic, Antimony, Copper, Sulphur and Carbon. — These
elements are seldom present in sufficient quantities in spelter to
affect its properties for the uses for which the metal is usually
employed. Arsenic, however, should be absent in zinc used for
generating hydrogen for use in lead burning, or autogenous
welding, otherwise it is often impossible to burn a strong seam.
It should also be absent in zinc intended for the precipitation of
gold in the cyanide process, as in treating the precipitate with
acid arseniuretted hydrogen is given off, and this has resulted in
several fatal accidents.

Tin and Aluminium should always be looked for in remelted
spelter. Tin tends to make zinc very hard and brittle in rolling.
Some brands of remelted spelter contain aluminium, usually
to the extent of about 0*3 per cent.

Small quantities of copper are not infrequently present in
remelted spelter.

147 L 2

CHAPTER IX

THE MARKETING OF ZINC

Grades of Commercial Zinc

THE quality of commercial zinc varies considerably according
to the method of production, but in many cases the sole practical
difference between ordinary commercial spelter and the much
more valuable fine-zinc is represented by the lead content. For
some industrial uses zinc is required in a state of fairly high
purity, consequently there is a good demand for high-grade
metal.

The brands of zinc produced by remelting scrap metal, &c.,
usually contain impurities and are of inferior quality.

The slab zinc is marketed under various names, which are
used by the different smelting companies to denote their products,
the quality of which is known to the users of zinc.

A large number of brands of spelter are made on the Continent.
Many of the works make two or three different brands, varying
in quality and price mainly according to the lead contents,
but in some cases dependent upon whether the metal is
higher or lower in iron. The grading of commercial zinc
according to the amount of impurity, especially lead, is
most desirable, and, as shown below, has been generally adopted
in America in recent years. In this country, however, a hard
and fast classification does not appear to obtain, and what are
described as good ordinary brands show a very large variation
in the proportion of lead. Furthermore, different consignments
of spelter of the same brand will often vary in this manner
to an undesirable degree.

In good ordinary brands (G.O.B.) of British spelter the lead
usually varies from 0-8 to 1-8 per cent, and the iron from 0-02 to

148

THE MARKETING OF ZINC

0-04 per cent. In Silesian unrefined spelter, as tapped in hand
ladles, the lead is usually higher, reaching over 2 per cent. In
some brands of American high-grade zinc lead is absent or does
not exceed 0-02 and the iron o-oi to 0-02 per cent. The brands
of electrolytic zinc seldom show higher purity than is obtainable
by modern fire refining. The purity in both cases is usually
guaranteed 99-95 per cent, of zinc.

The following analyses of British, Continental and American
brands of spelter may be taken as typical : —

ANALYSES OF COMMERCIAL ZINC.

Cad-

Zinc.

Lead.

Iron.

mium.

Tin.

Copper.

Brand.

Per

cent.

Central Zinc Co. (British)1 . .

98-642 j 1-205

0-06

0-089

0-004

V.M.G. (Belgium)2
Vieille Montagne (Belgium)2 . .

99-05 0-66
97-89 2-00

0-26
0-04

0-07

0-03

—

Freiberg (Saxony)2

98-84

1-03

0-04

0-02

0-07

— .

Lazyhutte (Upper Silesia)2 . .

97-85 I-I2

O'O2

0-017

—

— .

Lipine Electrolytic (Upper

Silesia)2

99.905

0-06

O-OI

0-005

0-02

- — •

Font-d'art (France)8

99.718

o-i35

O-2O

0-123

trace

Scrap3 . . . . . . . . 96-447

2-05

0-03

0-003

I-4I

0-06

The virgin spelter produced by the Central Zinc Company, at
Seaton Carew, Durham, is from Broken Hill ore.

The American Society for Testing Materials suggested in 1911
the following four grades for commercial spelter.

Grade.

Lead.
Per cent.

Iron.
Per cent.

Copper.
, Per cent.

Total
not over
per cent.

High grade . .
Intermediate . .

0-07

O-2O

0-03

|
0-05
0-05

O-IO

0-50

Brass special . .

0-75

0-04

0-75

I-2O

Prime Western

1-50

0-08

1 Moulden, Journal of Royal Society of Arts, 1916, vol. Ixiv, p. 512.
- Primrose, Journal of Institute of Metals, 1909, vol. ii, p. 234.
3 Jones, Journal of American Institute of Metals, 1915.

149

THE ZINC INDUSTRY

The figures represent the maximum percentage of impurities
allowable. This classification corresponds substantially with
the understanding among American zinc smelters.

The following table gives the analysis of typical commercial
samples of the various grades of American spelter l : —

Zinc.
Per cent.

Lead.
Per cent.

Iron.
Per cent.

Cadmium.
Per cent.

High grade

99-960

•010

•026

•040

,, ,,

99-945

•041

•014

— •

,, ,,

99-951

•°35

-014

- — -

Intermediate

99-896

•095

•009

— .

99-793

•190

-017

— .

99-746

•123

•Oil -I2O

Brass special

99-631

•343

•026

. »

99-5I3

'474

•013

i »

99-036

•680

•oio -274

Prime Western

99-045

•870

•062 -023

, ,,

98-253

-644

•013 1-090

. >»

98-641

1-270

•oio -079

98-503

1-448

•024 -024

Willemite (Eastern Penn-

sylvania) 2 . . . . 99-955

•039

•003 -ooi

and copper

•OOI

•002

The " Prime Western " brand corresponds with " good ordinary
brands " in European quotations and includes the bulk of
American spelter.

The grade produced in largest amount in America is " Prime
Western," a considerable part of which is used for galvanising
iron and steel wire and sheet. " Brass special " is used chiefly in
the manufacture of brass. The price of " high-grade " spelter is
usually 2 to 4 cents per Ib. more than that of " Prime Western."
The "high-grade" and "intermediate spelters" are made by
only a few smelters, but the "brass special" and "Prime
Western " are made by many concerns.

Sampling Zinc. — Slabs of spelter as supplied by the smelter
are not of exactly uniform composition, as the kettle into which
the metal is received from the furnace holds a relatively small
quantity, and the impurities passing over with the zinc vary in

1 G. C. Stone, Transactions of the American Institute of Metals, 1915,
vol. ix.

2 J. L, Jones, ibid.

150

THE MARKETING OF ZINC

amount in different parts of the furnace, according to the tempera-
ture of the retort. To ensure uniformity as far as possible, the
zinc should be tapped into large ladles or remelted in large pots
or furnaces before being cast into slabs for delivery.

Segregation of the impurities, however, invariably takes place,
and slabs of commercial zinc are rarely uniform in composition.
Under these conditions the sampling of the slabs is a matter of
considerable importance, although it does not always receive
the attention it deserves.

One slab out of every ten should be taken for sampling to
secure a trustworthy average of the shipment or consignment,
but this practice is not always carried out. American brass-
makers follow a time-honoured practice of sampling a carload
(about 50,000 Ib. of spelter in 820 to 960 slabs) by drawing 10 slabs
at random, and that practice has recently received the endorse-
ment of t.,e American Society of Testing Materials.

The sample for analysis is taken from the selected slabs either
by breaking a small piece off one corner of each slab or by
drilling right through each slab.

The latter method is the more satisfactory, provided proper
precautions are taken to prevent contamination of the sample
with iron from the drill. A twist drill, about f inch, is very
suitable for the purpose. It must be kept sharp and be
fed slowly enough to enable it to clear itself of all drillings.
If this is not done, the drillings are liable to pick up iron from
the drill in such a firmly adhering form that removal by means
of the magnet or otherwise is out of the question. Sampling by
sawing the slab completely through with a band saw, as is
frequently done in sampling pigs of lead, has been adopted in a
few cases with satisfactory results.

The Price of Zinc

When viewed over a considerable period of years, the market
value of spelter has, not unnaturally, fluctuated considerably.
When first produced it realised a high price, which rapidly fell
as production increased and no new output for its consumption
opened out.

In renewing the price of zinc Moulden points out that in 1807 l

1 The prices quoted, 1807 to 1850, are based upon figures as given by
Liebig : " Zink und Cadmium," Leipzig, 1913 (per J. C. Moulden).

THE ZINC INDUSTRY

it was about £40 per ton, rose in 1808 to £84 per ton, and then
fell steadily as production overtook demand, until in 1820 it
stood at no more than £n.

The extension of sheet rolling caused the price to rise until
in 1825 it reached £30 ; it fell again as production increased, and
between 1830 and 1836 fluctuated between £10 and £19. It
again fell to £10 in Breslau (the Silesian centre) in 1848. In
1850 it was quoted at about £16, and from that time onward
to 1913 the yearly average fluctuated between £13 195. nd.
(the lowest touched in 1885) and £27 is. $d. in 1906.

Moulden remarks that the general tendency of late years has
been towards a distinctly higher average level. For a very long
time low wages and easily won and treated ores kept the price
low. As wages increased and difficulties of treatment arose the
improvements in metallurgical efficiency and extraction kept
pace up to a certain point and compensated the producer. Beyond
this point there was bound to be a rise in average value, and this
is clearly reflected in the fact that only twice since 1898 has
the average price been below £20, and never since the close of
1902. Prior to the war industrial conditions had reached such
a point that, broadly viewed, a £20 market was considered by
smelters to be unremunerative and distinctly unprofitable in
particular for those concerns which did not themselves possess
mines.

The establishment of the Zinc Conventions (see p. 155) and
the German control of Australian concentrates, not unnaturally,
had some influence in regulating the price of spelter.

" The Metallgesellschaft, acting on behalf of the German
Group, purchased for a number of years the whole supply of
Australian zinc concentrates, and the price was regulated by
the average of the mean daily quotations made on the London
Metal Exchange. The Metallgesellschaft, through its Australian
connection, the Australian Metal Company, and Hirsch & Com-
pany, through their Australian representative, arranged the
contract with the Broken Hill Groups.

" The contract was made so that if the price of spelter rose
above £22 or £23 a ton, any excess above that price was divided
equally between the buyer and the seller. That contract having
been signed, the European Spelter Convention was formed about
the middle of January, 1909. Spelter at that time was £21 IQS.
a ton, and it is now common knowledge that it was forced up to

152

THE MARKETING OF ZINC

more than £27 a ton. The higher price brought a remarkable
increase in production, so that the price, after touching more
than £27 a ton in 1911 and 1912, fell during the first half of 1913
to £22 a ton, and during July and August of the same year to
about £20 IDS. a ton."1 Thus the successful negotiations and
contracts for the Australian was a mere question of £ s. d. or
who would pay the highest price.

Owing to the conditions that prevailed consequent upon the
outbreak of war, the selling price of spelter appreciated to more
than five times its pre-war figure. During 1915 the price of the
metal was subject to more violent fluctuations than have been
recorded during the past fifty years.

THE HIGHEST, LOWEST, AND AVERAGE PRICE PER TON OF COMMERCIAL
METALLIC ZINC IN THE LONDON MARKET FROM THE YEAR 1900

TO 1917.

English
spelter.

Foreign
spelter.

Year. j

Highest.

Lowest.

Average.

£ s. d.

1900

22 15 0

18 10 o

20 16 o

20 13 5

1901

18 18 9

16 o o

17 14 5

17 7 6

1902

19 17 6

16 7 6

19 3 8

18 14 8

1903 .. . .

23 18 9

19 15 o

21 12 0

21 4 8

1904

25 10 o

21 2 6

23 2 II

22 l8 0

1905

29 2 6

23 5 o

26 0 0

25 15 2

1906

29 10 o

24 o o

27 12 4

27 8 o

1907

28 2 6

19 10 o

24 II I

24 9 6

1908

21 17 6

18 o o

21 0 II

20 17 i

1909 . .

23 6 3

21 I 3

22 16 6

22 13 0

1910

24 5 o

21 12 6

23 19 o

23 12 0

1911

27 17 6

22 17 6

25 3 9

25 16 7

1912

27 12 6

25 o o

26 3 4

27 4 2

1913 ••

. — .

— 1

22 14 3

23 15 6

1914 ••

34 o o

21 6 3

1915 ••

I2O O O

28 o o

Average

£66 13 8

1916

110 0 0

44 o o

1917 ••

57 o o

44 o o

It rose gradually from £28 per ton in January of that year to
£120 in June ; then a reaction occurred, and by August the price
had fallen to £55 a ton. Thence up to November there was

1 H. Kaye, Journal of the Institute of Metals, 1916, vol. xvi, p. 186.

153

THE ZINC INDUSTRY

another increase until the price was again more than -fioo. In
1916 the highest price reached was £110, and the lowest £44,
while in 1917 the price rose to £57 and went as low as £44. The
year closed with zinc at about £52 per ton.

The yearly and monthly average prices of spelter for the ten
years prior to the war are given in the table on p. 153.

In normal times the prices of metals reflect, in a large measure,
the relation between production and consumption, but for some
time past such cannot be said to be the case, as the metal industry
is now controlled by the Government, almost all the available
supply being devoted to the purposes of war, the ordinary trade
requirements having, naturally, to be left unfilled.

The World's Zinc Markets

London is the principal European zinc market, the price of
the metal being quoted in £ s. d., according to the prevailing
prices for G.O.B. (" Good ordinary brands " or " Good ordin-
aries "), and a slightly higher quotation for " Specials," the purer
quality of zinc. As previously stated, many of the smelters,
both in this country and abroad, make two or three different
brands of zinc, varying in quality mainly according to the lead
contents, but in some cases dependent on the iron content.
They are sold at various prices, the better grades of metal natu-
rally commanding higher prices. British spelter is usually quoted
under the heads of " Ordinary brands/' " Special brands," and
" English Swansea."

The several selling centres for zinc in the German Empire
are Breslau, Cologne, and Frankfort-on-Main. The price is
always quoted in marks per ton, the difference in price between
each brand being usually I or 2 marks.

The American zinc market is entirely independent of that of
the rest of the world, as, under normal conditions, America is
not favourably situated to compete with the British and Conti-
nental markets. The conditions relating to the marketing of
zinc in America have been summarised recently by C. H. Fulton 1
as follows : —

1 Technical Paper 83, Bureau of Mines, Washington, 1915, p. 38.

154

THE MARKETING OF ZINC

" The main market or basing point for spelter is St. Louis,
Missouri, for the reason that the great zinc fields and a large
number of the smelting plants for zinc are situated not far from
St. Louis. However, the large consumption of spelter is at places
between St. Louis and New York, and it is sold in New York
on a St. Louis basis, the quotations being given in cents per Ib.
The New York price is the St. Louis price plus 15 cents per
100 Ib., which is the freight rate on spelter from St. Louis to New
York. The American market is in part independent of the
European market, because spelter is protected by an import duty
of 15 per cent, and zinc in ore by a duty of 10 per cent, ad
valorem.

" In the marketing of zinc, it is customary for the producer
to sell direct to the manufacturer. This policy, however, in
view of the large number of producers, is not nearly so closely
followed as in the selling of copper, and some of the producers,
particularly the smaller ones, sell to anyone who cares to purchase.
This condition of course gives rise to more speculation in zinc
than in copper. The real spelter market is established by the
private transactions of producer and consumer, and any informa-
tion as to the state of the market can come only from them.
The facilities for exchanging information in the spelter market
are not as good as those in the copper market, and hence transac-
tions between producer and manufacturer often show considerable
difference in price." The four brands of spelter on the American
market, with their names and permissible proportions of impuri-
ties, have been given on p. 149.

The Spelter Convention

Prior to the outbreak of war the spelter market was very
largely controlled by the Spelter Convention, an association
of zinc smelters formed in 1909 and elaborated in 1910. Separate
syndicates were formed for each zinc-producing country, and
included all the German, most of the Austrian, Belgian and
French, and many of the British smelters. The Convention
consisted of three groups : —

Group A, known as the Verband, or German Syndicate, com-

155

THE ZINC INDUSTRY

prised the associated German and Belgian makers, whose output
was disposed of by a joint selling office.

Group B comprised certain Belgian and French producers.

Group C comprised the British producers.

The two latter groups constituted the International Spelter
Syndicate, which on December i8th, 1913, was, with slight
changes, renewed on the old conditions until April 3oth, 1916.
The German Syndicate was also prolonged until the same date.

The object of the Convention was to control output by fixing,
within certain limits, the individual production of its members,
and to ensure a uniform mode of selling, and, if the market
showed that the demand was not keeping pace with the output,
to restrict the latter.

On the Continent, the sale of the metal was in the hands of
the leading trading companies in metals and minerals, who,
jointly with the producers, fixed the selling prices and the
quantities to be produced by each works. Over-production
above the quantities fixed by the board of management was
subject to heavy penalties. The total of the amounts realised,
after deduction of selling and administration expenses, was
distributed amongst the various works in accordance with the
deliveries made by them, and in taking into consideration certain
geographical positions and superior qualities of spelter produced,
various premiums were admitted. The smelters with their own
mines (" Erzhuetten "), on the other hand, paid a certain amount
for each ton of ore produced and treated by them to make up
for the advantage they had against the " Lohnhuetten," or
customs works, who bought their ore in the market.1

Restriction of output came into force when the average price
of spelter in the London market had remained at £22 or under
for two months, and when the unsold stocks, which were taken
quarterly, amounted to 50,000 tons.

The British and French smelters were bound to a joint restric-
tion of output in certain circumstances, but they had more
liberty of action than the other members, being free from selling
restrictions. The German smelters were under the most stringent
rules as regards production, prices and agencies through which
sales could be made.

1 J. Gilbert, Mining Journal, London, 1916, vol. cxiv, p. 497.

156

THE MARKETING OF ZINC

American smelters were not included in the Convention, as
the home consumption at that time equalled the production,
and it was therefore unlikely that they could influence the
European market.

Pursuant to the above provisions the International Syndicate
on May 26th, 1913, reduced prices by 505. per ton, and the London
quotation went down to £23. On October ist, 1913, the Conven-
tion ordered a reduction in output of 8 per cent.

" On the whole," according to J. Gilbert,1 " the Spelter Syndicate
may be said to have served the interests of European producers
to some considerable extent by regulating the uniformity of
the supply, which has permitted a steady progress of the industry,
with fairly uniform remuneration of capital and labour, and with-
out unduly exposing it to the inveterate risk of speculation, which
very frequently most radically interferes with the interests of
both producers and consumers of certain commodities. Unfortu-
nately, however, so far as British interests are concerned, one
all-important feature has been overlooked, and that is the fact
that, whilst British consumers of spelter absorb about 40 per
cent, of the European production, the British production of
spelter hardly exceeds 10 to 12 per cent, of the European output."

The Production and Consumption of Zinc

Production. — Owing to the complications introduced by primary
and secondary and redistilled hard spelter, &c., it is very difficult
to ascertain with accuracy the world's yearly production of zinc.
The bulk of the metal will, however, have been produced direct
from ore, possibly about 75 per cent., leaving 25 per cent, for
remelted metal recovered from scrap metal, galvanisers, ashes,
&c. The world's output of spelter from the early days of the
industry to modern times has been given previously. The
quantities of spelter produced by the chief countries for the ten
years ending 1913 are shown in the following table.

1 J. Gilbert, Mining Journal, London, 1916, vol. cxiv, p. 487.

157

THE ZINC INDUSTRY

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III

THE MARKETING OF ZINC

From the figures on p. 158 it will be seen that the absolute and
relative contributions of Europe and the United States to the
world's production of spelter for the years 1910-1913 are as
follows : —

Europe.

United States.

Year

Per cent, of

Metric tons.

world's

Metric tons.

world's

output.

IQIO

565.500

69-3

250,600

30-7

IQII

632,900

70-2 267,500

29-7

1912

661,100

67-6 3I4.500

32-2

1913

673,900

67-5

320,300

32-1

Consumption. — One of the difficulties in estimating the amount
of zinc used in the Arts is that variable proportions of old material
are used with new material, and in consequence the consumption
sometimes exceeds the total production for the year. The esti-
mates of consumption take no account of any stocks which may
exist, and hence, theoretically, the total consumption should
yield the same figures as the total production.

Taking into account stocks at German works, the actual con-
sumption of spelter in Germany during 1911 was about 217,900
tons, in 1912 about 220,800 tons, and in 1913 about 221,800 tons.
When the stocks of other countries are taken into account, the
returns show that prior to the war the production for the years
named was in excess of the consumption.

The following table shows the absolute and relative contribu-
tions of Europe and the United States to the world's consumption
of spelter for the years 1910-1913.

Europe.

United States.

Year.

Per cent, of

Metric tons.

world's

Metric tons. world's

output.

1910 . .

599,4°°

73'4

244,500

29-9

1911

652,400

72-3

251,600

27-8

1912

667,700

68-2

312,900 31-9

1913

675,000

67.7

313,300 31-4

159

THE ZINC INDUSTRY

The world's consumption of spelter during the ten years imme-
diately preceding the war is shown in the following table.

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III It II I

160

CHAPTER X

THE INDUSTRIAL APPLICATIONS OF ZINC

THE most important use of metallic zinc is in galvanising, which
probably consumes more than 70 per cent, of the total output.
The manufacture of brass probably utilises another 20 per cent.,
while the remaining 10 per cent, is used for conversion into
sheets and for minor purposes, such as the production of alloys
other than brass.

Galvanising. — The process of zincing, or, as it is termed,
galvanising, which was discovered by Crawford in 1837, consists
in depositing a very thin coat of zinc on iron, whereby the latter
is preserved from oxidation by the atmosphere. In the United
Kingdom galvanising has become an important branch of metal-
lurgical industry and is very extensively practised, the chief
centres of production being the Birmingham, Wolverhampton
and South Wales districts.

Galvanising may be effected by the method known as hot
galvanising (immersion in molten zinc), by the electrolytic pro-
cess, by Sherardising, or by Schoop's metal-spraying process.

The hot galvanising process was, however, responsible for the
production of practically all the 850,000 tons of galvanised sheets
and wire exported from the United Kingdom in 1913.

In this process the iron is first freed from scale by immersing
(" pickling ") in hydrochloric acid, then washing well and scouring
with sand. After cleaning, the plates or other articles are
immersed in the galvanising bath, which is contained in a
wrought iron pot, and consists of molten zinc covered with a
layer of ammonium chloride.

The strength of acid used for pickling varies with the nature
of the work. In the United Kingdom a 20 per cent, solution of

161 M

THE ZINC INDUSTRY

hydrochloric acid is generally used for iron sheets, and acid of
12 per cent, strength for iron wire and tubes. The pickle is
used cold, or nearly cold, and the operation is complete in a few
minutes. At some works, particularly on the Continent, dilute
sulphuric acid is used in place of hydrochloric acid for reasons of
economy, but in this case a longer immersion is necessary. The
temperature of the galvanising bath determines the thickness of
the zinc coating ; the hotter the bath the thinner the deposit. The
solvent action of zinc on iron, according to Diegel,1 increases
gradually up to about 490° C., above which temperature it rises
very rapidly, being thirty times greater at 530° C. than below
490° C.

The iron sheets may be passed, after their passage through
the bath, between rolls or wire brushes to remove superfluous
zinc, and thus reduce the consumption of zinc. This treat-
ment considerably improves the surface of the sheets.
Zinc of good quality should be used for the galvanising bath,
as the presence of lead exceeding 2 or 2-5 per cent, renders the
zinc unsuitable for galvanising, the lead being easily dissolved
by most soft waters, thus exposing the surface of the galvanised
metal and hastening corrosion. Galvanised sheets often exhibit
a beautiful moirt-metallique surface, due to the crystallisation of
the zinc. When it is especially desired that the finished articles
shall have a spangled appearance, from 2 to 3 per cent, of tin is
sometimes added to the zinc bath. The addition of aluminium
is said to increase the fluidity of the galvanising bath, owing
to its deoxidising action, and also to its influence in effecting
the separation and precipitation of the iron that accumu-
lates in the bath. The aluminium should be added in
the form of a zinc-aluminium alloy with a melting point
below 480° C. Corrugated iron sheets form a considerable portion
of the galvanising trade ; these are often galvanised plain and
then passed through the corrugating machine. The galvanising
of iron wire, such as is employed for fencing, signal wires, &c.,
is performed with great rapidity, the coiled wire being annealed
at the same operation. For this purpose the coiled wire is
drawn through a furnace of such length that the wire in its
passage through it is heated to redness, whilst the heated wire,
as it passes out from the furnace, is directed by guide pulleys
through a reservoir of dilute sulphuric acid (pickle), which has

1 Journal of the Society of Chemical Industry, 1915, vol. xxxiv, p. 1147.

162

THE INDUSTRIAL APPLICATIONS OF ZINC

the effect of cleaning off any scale. On leaving the pickle it
passes through a quantity of sand, whereby the wire acquires a
clean metallic surface before it enters the bath of molten zinc.
In this manner, whilst one end of the wire is still passing
through the annealing furnace, the other extremity is being
wound on to a drum in its galvanised state.

Owing to the great ease with which zinc is attacked by acids,
galvanised iron is not adapted as a constructive material where
it would be exposed to acid vapours.

In addition to sheets and wire, the process of galvanising is
applied to chains, links, and many other articles requiring to
be protected from corrosion.

The hot galvanising process yields two by-products : (i) hard
zinc and (2) flux skimmings. The former is an alloy of zinc
and iron, containing from 2 to 5 per cent, of iron, resulting
from the gradual contamination of the zinc bath with iron.
Being heavier than zinc, this alloy sinks to the bottom of the
bath in pasty masses, and is removed from time to time by means
of a perforated iron ladle, and cast into plates, which, when
broken, exhibit a close-grained fracture with black spots character-
istic of zinc containing iron. Part of this alloy passes into
commerce for use where a zinc-iron alloy is required, and the
remainder is liquated to separate as much zinc as possible.
For this purpose the alloy is usually remelted at a high tem-
perature, when it separates into two layers, the top layer
consisting of tolerably pure zinc, which is carefully ladled off.
The bottom layer is much less fusible, and forms a hard
crystalline or granular material of the colour of zinc, but less
lustrous. This ferriferous zinc is very friable, and frequently
exhibits surface colorations of great beauty ; it contains about
7*5 to 9 per cent, of iron, and is sold to the zinc smelters, who
recover the zinc by a special redistillation.

The scum that accumulates on the surface of the galvanising
bath and known as " flux skimmings " is removed from time to
time. It consists of chloride and oxide of zinc together with
some ammonium chloride and dirt. It is sold to the smelters,
who treat it, usually by distillation, for the recovery of the zinc.

The disposal of the waste pickling liquors, which contain
about 15 per cent, of hydrochloric acid and 10 per cent, of iron,
chiefly as ferrous chloride, has caused considerable trouble in
many localities where galvanising is carried on, and special

163 M 2

THE ZINC INDUSTRY

processes have been devised to deal with them. Hitherto the
usual system has been to neutralise the acid with lime and
subsequently to roast the precipitate of ferrous hydroxide so
obtained in order to convert it into red oxide of iron, which is
sold.

The great increase in the price of zinc since the outbreak of war
seriously affected the galvanising industry and led to the
adoption of other methods and of substitutes, such as electro-
galvanising, which consume much less zinc, and galvanising with
lead, either by the hot process or by electro-deposition. Although
it is not easy to disturb the settled demand for a world-wide
commodity such as galvanised sheets, there are obvious possi-
bilities in substitutes, once the buyer is familiarised with them
and finds them cheaper. Experience shows that substitutes
for zinc will probably hold some of the ground they have
temporarily acquired.

The electro-galvanising process has gained considerable favour
in recent years, and its use is rapidly extending for certain classes
of work, as it possesses several important advantages over hot
galvanising. These may be summarised as follows : (i) greater
economy in the use of zinc, as a much thinner deposit than that
afforded by hot galvanising is sufficient to prevent rusting ;
(2) more complete control of the thickness of the coating on
various surfaces ; and (3) suitability for articles, such as steel
springs, which have been subjected to special heat treatment
and must not be heated to the temperature of molten zinc.
Another advantage claimed for electrolytic galvanising is that it
reveals defects, such as fine cracks, &c., in the iron, which
would be concealed by hot galvanising. On the other hand,
the electro-galvanised surface is dull or " dead " and not so
pleasing in appearance as that produced by the older method.

Although a large number of solutions have been tried for
electro-zincing, the general opinion amongst practical operators is
that solutions of the sulphate, either alone or with other salts,
give for general purposes the most trustworthy results, with the
minimum of trouble in working.1 In practice, the zinc is usually
employed either in the form of a neutral solution of the sulphate
or dissolved in excess of caustic soda.

" Sherardising." — In the process of coating iron and steel with
zinc, introduced by Sherard Cowper Cowles, and known as

1 " Electro-Plating," Barclay and Hainsworth, London, 1912, p. 312.

164

THE INDUSTRIAL APPLICATIONS OF ZINC

" Sherardising," the articles, after being thoroughly cleaned by
pickling, &c., are heated in metal drums, or boxes, in contact
with zinc dust at a temperature of from 260° C. to 425° C.
Vaporisation of the zinc dust takes place, the metal vapour then
condensing on the surface of the iron articles. A zinc dust
having a high metallic content will give the best coating. The
condensed zinc slowly combines with the iron, giving a coherent
protective coating that is highly resistant to corrosion.

The iron content of the Sherardised coating is a function of
the temperature. The process is therefore carried out at the
lowest temperature that is economically possible to secure a low
iron content in the coating, since a high iron content is detri-
mental to the weathering properties of the coating.

The Sherardised surface is light grey in colour, with a dull or
matte finish, but it is capable of receiving a high polish and
made to resemble nickel plate. The process is economical and
yields a superior product, and will doubtless receive more atten-
tion in the future than has been hitherto accorded to it. It is
specially adapted for coating articles having a pattern or design
on the surface which would become filled up and obliterated if
the ordinary galvanising process were employed. Iron screws
which have been galvanised by Sherardising are ready for use
without further treatment. Narrow tubes can be galvanised
inside by Sherardising, and this process has been used for coating
with zinc the iron 5 pfennig pieces recently introduced in the
coinage system of Germany.

The process of galvanising, patented by Schoop, of Zurich,
consists in projecting a spray of pulverised zinc on to the goods,
previously cleaned and warmed, until a zinc deposit about
o-i mm. thick is produced. The adherence of the deposit is
said to be perfect. In the latest development of the spray pro-
cess the zinc in the form of strip or wire is fed at a uniform rate
into an oxy-hydrogen or other flame (or even an electric arc)
sufficient to melt it readily. As fast as the metal melts a stream
of compressed gas directed on it carries it away in a state of
fine subdivision on to the surface to be coated. In practice, a
specially constructed " metal spray pistol " is used for producing
the spray. Very promising results are said to have been obtained
by this process in Belgium and France, where it is in use on a
large scale.

165

THE ZINC INDUSTRY

Rolled or Sheet Zinc

Zinc lends itself well to rolling into sheets when the operation
is carried out at a temperature between 100° C. and 150° C.,
within which range the metal is most malleable and ductile. In
spelter intended for rolling, a small percentage of lead is desirable,
as it improves the rolling qualities of the zinc, but the amount
should not exceed i per cent. The rolled zinc of commerce
is therefore a nearly saturated solution of lead in zinc,
since it usually contains I per cent, of lead. Iron increases
the hardness and impairs the malleability of zinc and should not
exceed 0-15 per cent. In practice, it is usual partially to refine
the spelter by liquation, so as to reduce the lead and iron
to the minimum practicable by such methods, and when the
refining has been properly conducted these amounts have little
or no effect upon the malleability and ductility of the zinc.
The metal to be used for rolling into sheets is cast in open moulds
into flat ingots or plates which, whilst still hot and at the proper
temperature, are rapidly passed through the rolls until the
correct gauge is attained. For convenience, the ingot moulds
are sometimes arranged in a circle on a rotating table.

Most of the zinc rolling is done on the Continent in Silesia and
Belgium. The output of sheet zinc in Belgium in 1913 was
51,500 metric tons. A small quantity is rolled in the United
Kingdom, chiefly at Birmingham, where zinc was first rolled
early in the last century. There are also zinc rolling mills in
the United States.

Prior to the war it was usual to import Continental zinc for
rolling in this country, as it contained more lead than most of
the British brands, which after refining are relatively free from
lead, and are mainly employed for the production of alloys. It is
customary when rolling Continental zinc to remove the excess of
lead by liquation, as previously stated. In addition to the small
amount of zinc rolled in this country, more than 20,000 long tons of
foreign sheet zinc are annually imported into the United Kingdom.
It would thus appear that there is ample scope for the extension
of the British zinc rolling industry. A very large proportion of
the zinc sheeting annually produced is employed for roofing
purposes, mainly on the Continent. The metal is used either
in the original sheets, or in the form of ornamental stamped

166

THE INDUSTRIAL APPLICATIONS OF ZINC

tiles, which are nailed to the roof in an inclined position in the
same way as slates. As a roofing material, sheet zinc is durable,
light and efficient. Although up to the present it has found little
application in the United Kingdom for roofing, its uses for this
purpose have become so extensive in Continental countries that
the spelter market is very materially influenced by the pros-
perity or otherwise of the general building trade.1

Thin sheet zinc finds application for a variety of purposes.
In this form it lends itself readily to stamping in dies,
and stamped ornaments in zinc were first produced in 1852.
Within recent years it has found very considerable use for
ceilings, the metal being stamped with varied ornamental designs
in relief. It finds employment in the manufacture of many
articles in ordinary domestic use, such as bath-tubs, pails, toys,
£c. Metal of thinner gauge is used for the lining of air-tight
wooden cases, hermetically sealed by soldering, for export to
tropical countries. When perforated, sheet zinc is used for
screens, sieves and other purposes. Rolled zinc plates of specially
high quality find important use in the photographic reproduction
process known as photo-zincography and in photo-etching.

Hot zinc sheets with a fine smooth polished surface are employed
for producing the satinised surface finish on the better-class
papers.

Thick rolled zinc plates, sawn to suitable sizes and drilled for
bolting, are used to a considerable extent in marine boiler work
to prevent corrosion of the boiler plates. For this purpose the
zinc is bolted into position in different parts of the boiler, and
owing to its being highly electro-positive it is first attacked by the
corrosive influences and can be renewed when necessary. It is
essential, however, that thorough metallic contact between the
surfaces should be made to obtain full advantage of the pro-
tective influence of the zinc.

Zinc Castings

The use of zinc in the foundry is somewhat limited, the demand
for the cast metal being very small. It contracts but slightly
on solidification, and. is thus well adapted for castings. The
castings made at a high temperature are brittle and largely

1 J. C. Moulden, loc. cit., p. 522.

167

THE ZINC INDUSTRY

crystalline ; but when cast near the solidifying point they are
more malleable. Overheating of the metal, with its attendant
losses, should be carefully avoided. Ammonium chloride (sal
ammoniac) is recommended as the best flux, its action being to
convert the floating dross from a pasty mass to a " dry
dust."

Aluminium is recommended as the best deoxidiser, to be added
after skimming, in the proportion of o-ooi per cent., and in the
form of thin sheet clippings ; the fluidity of the molten zinc is
thus increased.1

Owing to the facility with which lead segregates, especially
if the metal is poured at a high temperature, no brand of zinc
containing more than 0-5 per cent, of lead should be used in the
foundry.

Dies or blocks upon which hats are shaped are made of cast
zinc. Cast zinc dies are used in the dental laboratory for swaging
artificial metal-dentures. It is also employed for monuments,
statues and tombstones, under the name of white bronze.

Spelter is also largely used for the production of " slush "
castings for ornamental purposes.

In these, the metal in the mould is poured back into the
ladle as soon as a thin layer has solidified on the face of the
mould. These hollow castings must be sound, not merely
for strength, but because they are all ornamental in character,
and are usually required to be subsequently plated. The
moulds are usually made of bronze, and many of the shapes
are such as to cause excessive strains in the solidified zinc. The
castings are polished and plated or otherwise finished. Makers
of intricate slush zinc castings find it necessary to use
metal of high grade, otherwise the castings are very liable to
crack. Indeed so much is this liability to crack an indication of
the quality of the metal that a number of the makers of high-
grade zinc in America use the slush mould as a means of testing
their product.

Cast zinc rods find extensive application in battery cells for
electrical work. Rods are also prepared for this purpose by
rolling, or by extruding the metal. Zinc of high grade should
be used in their manufacture, as the life of such rods is much
longer than of rods made from ordinary brands of spelter.

The employment of zinc for the manufacture of seamless pipes
1 The Foundry, 1915. vol. xliii, p. 233.

168

THE INDUSTRIAL APPLICATIONS OF ZINC

for water supply has been advocated in recent years.1 The pipes
are made from pure " hard " zinc and have a diameter up to
80 millimetres. They can be tin-lined if required. Two pipes
can be joined in the usual manner by widening the end of one
and inserting the end of the other, or by covering the adjacent
ends with a sleeve, and soldering. Tin solder is used, preferably
with a stearine flux. The manufacture of the pipes is simple,
and their bending easy. The pipes are as useful for water supply
as lead pipes, and have the advantage of being much safer from
a hygienic point of view, as no injury has been found to a rise from
the traces of zinc which are dissolved by water. Zinc is cheaper
than lead for this purpose, and on account of its lightness the
pipes do not require such strong wall supports. A pressure of
500 atmospheres is required to burst the pipes. These pipes
cannot, however, be used for a hot water supply on account of
the great expansion of zinc. In some recent tests by Rinck2
tap water of medium hardness was sealed up in large zinc pipes
with air excluded. After a year the amount of dissolved zinc
was 2 to 3 milligrammes per litre. Physiological tests over a
long period with water containing 7 to 8 milligrammes of zinc
per litre gave no indications of injurious results.

Other Uses of Zinc

Metallic zinc plays an important part in several metallurgical
operations, notably in the precipitation of gold and silver in
the cyanide process, the desilverisation of argentiferous lead
by the Parkes process, and the reduction of silver chloride in
gold refining.

Large quantities of zinc are used annually in South Africa
and elsewhere for precipitating gold from cyanide solutions by
means of zinc shavings. The precipitation is usually effected
in wooden or steel troughs (known as zinc boxes) containing
shavings of zinc coated with precipitated lead, formed by dipping
the shavings into a strong solution of lead acetate. The zinc
shavings are very thin and light, and are carried on iron gratings

1 Wittus, Jour. Gasbeleucht. 1913, vol. Ivi, pp. 936-937. Abstract,
Journal of the Society of Chemical Industry, 1913, vol. xxxii, p. 957.

2 A. Rinck, Zeit. Untersuch. Nahr. Genussm., 1914, vol. xxviii, pp. 99-103.
Abstract, Journal of the Societv of Chemical Industry, 1914, vol. xxxiii,

P. 883.

169

THE ZINC INDUSTRY

through which the auriferous solution passes. The gold is
precipitated on the zinc as a black mud, and is recovered by
dissolving out the excess of zinc with acid. After drying, the
gold mud is melted with fluxes and the resulting metal refined.
From 5 oz. to 16 oz. of zinc shavings are generally needed for each
ounce of gold recovered. The consumption of zinc in South
Africa, chiefly for this purpose, amounted to 4,867 tons in
1914.

The employment of zinc in the desilverisation of lead is based
on the fact that when molten zinc is stirred with a bath of
argentiferous lead, which is afterwards allowed to cool, a crust
forms on the surface consisting of zinc alloyed with silver and
any gold and copper that may be present.

In the Parkes process, the solid zinc in slabs is thrown on the
surface of the molten lead, and when it is melted the mixture is
well stirred and then allowed to cool. The total amount of
zinc added varies according to the content of silver, but is usually
from ij to 2 per cent, of the weight of the argentiferous lead,
and it is added in two or three lots, as several treatments with
zinc are necessary to remove all the silver. The zinc crusts
that form on the surface are removed by means of perforated
ladles, the crusts being kept separate.

Fresh additions of zinc are made until the lead contains only
about one-sixth of an ounce (0-0005 Per cent.) of silver per ton.
The zinc crusts, which are largely contaminated with lead, are
submitted to liquation, whereby the lead separates and flows
away, leaving the enriched scum behind.

The rich scums are distilled so that a large proportion of the
zinc is recovered and is available for further use. The residue
consists chiefly of lead, and contains from 5 to 10 per cent, of
silver, which is recovered by cupellation. It is essential that
fairly high-grade zinc be used for the Parkes process, as certain
impurities, particularly iron, cause a much larger consumption
of zinc. The process is carried out in large cast iron pots holding
as much as 50 tons.

Zinc plates are used to a limited extent for the reduction of
silver chloride resulting from the refining of gold. For this
purpose the silver chloride is melted and cast into slabs, which
are encased in flannel bags and boiled in water to remove base
metals. The slabs are then arranged alternately with zinc plates
in a tank of acidulated water, whereby the silver is reduced by

170

THE INDUSTRIAL APPLICATIONS OF ZINC

electrolytic action. In modern practice, however, iron plates
have been substituted for those of zinc.

Attention has already been directed to the use of zinc balls
for the precipitation of impurities in solutions that are to be
submitted to electrolysis. Recently the use of zinc balls for the
precipitation of gold in cyanide solutions in place of zinc shavings
has been suggested and introduced at several mines.

Metallic zinc has also been used for coinage. A new coin
consisting of pure zinc, and representing in value the ^-^th part
of a piastre, was legalised in 1905 for circulation in Indo-China.1
In that year 60,000,000 pieces, valued at £21,600, were struck
at the Paris Mint.

Zinc Dust (Blue Powder)

There is a limited market for zinc dust, which, as previously
pointed out, is a by-product from the distillation process. When
zinc vapour is cooled too rapidly after distillation, or if it becomes
too largely diluted with other gases, it condenses, not as fluid
metal, but in the form of a fine bluish-coloured powder, consisting
of an infinite number of minute globules coated with oxide, which
prevent it from coalescing by ordinary means. Some of this
substance, which is known as " Zinc Dust," " Blue Powder," or
" Poussiere," is always formed during the process of distillation,
and is usually found in the " prolongs " beyond the condensers.

The amount produced varies from 3 to 10 per cent, of the total
zinc present when retort smelting is used, but with electro-
thermic processes the quantity is usually much larger.

The commercial value of zinc dust depends upon its content
of metallic zinc, and the best grades contain from 86 to 92 per
cent, of zinc in the metallic state.2

The commercial standard is that it shall pass a loo-mesh
sieve and not contain more than 10 per cent, of zinc oxide.

Zinc dust is considerably more active chemically than spelter,
being oxidised readily, and having the power to absorb hydrogen.
On this account it finds many uses in chemical industries, being
used to discharge locally the colour of dyed cotton goods and in
the preparation of the indigo vat. It is used as a precipitant for

1 Thirty-sixth Mint Report, 1906, p. 31.

2 J. C. Moulden, loc. cit., p. 524.

THE ZINC INDUSTRY

the removal of copper, antimony, arsenic, &c., from electrolytic
solutions containing these and other metals.

It has also been used for the recovery of gold and silver from
cyanide solutions of these metals, for which purpose it has been
stated to be more efficient than zinc shavings. Latterly it has
found increasing favour for this purpose, as the small amount
of lead it usually contains acts beneficially in promoting more
rapid and complete precipitation of the gold and silver.

Reference has already been made to its use in the Sherardising
process.

Care has to be exercised in the storage of zinc dust, owing to
the readiness with which it will fire if exposed to moist air, or
wetted, when in bulk. Serious fires and even explosions have
been caused in this manner.

172

CHAPTER XI

INDUSTRIAL ZINC ALLOYS

ZINC enters into the composition of a number of important
alloys, to which, when present in certain proportions, it com-
municates hardness without impairing the malleability of the
alloy. In larger proportions it often renders the alloy
brittle.

Owing to the comparatively low melting point and volatility
of zinc, the preparation of its alloys requires considerable care
to prevent unnecessary loss of the metal.

Modern research has shown that the mechanical properties of
metals and alloys are materially influenced by the presence of
small quantities of impurities, and has emphasised the necessity
of employing pure metals in the preparation of alloys. This has
led, in the case of zinc alloys, to an increasing demand for zinc
containing less lead and other impurities than are usually present
in commercial spelter.

The economy and other advantages resulting from the use of
high-grade zinc for alloying purposes are so great that brass and
other alloy makers who have once employed it will never resort
to ordinary spelter if they can help it. To meet this demand
various works in the United Kingdom are producing a consider-
able amount of high-grade metal by distillation, and also by
electrolytic processes.

There are but few alloys in which zinc is the main constituent,
the chief being the so-called anti-friction metals, but in smaller
proportion zinc is a valuable constituent in several very useful
alloys.

The alloys of industrial importance in which zinc is a con-
stituent are (i) those consisting of.zinc and copper, constituting

:I73

THE ZINC INDUSTRY

the numerous varieties of brass ; (2) those consisting of copper,
zinc, nickel, forming the so-called " German or Nickel Silvers " ;
and (3) zinc with tin and other metals known as " anti-friction
metals."

Brass. — Brass was first made by the Romans shortly before
the Christian era, and was used both for coins and orna-
ments. The ancient name of the alloy was latten, which
is still retained in the French word laiton. In the Middle
Ages the Germans were famous for the production of brass,
which was imported into this country, principally from
Cologne, chiefly in the form of rectangular pieces known
as Cullen plates ; this was employed for the so-called
" brasses " of churches, particularly in the Eastern Counties.
More than 4,000 such brasses are known to exist in various
churches, &c., in the United Kingdom, which is far richer in
this respect than any other country. The first works for the
production of brass in England are stated to have been erected
by a German, at Esher in Surrey, about the middle of the seven-
teenth century, copper being imported from Sweden for its manu-
facture. Its manufacture was started in Bristol in 1702, and
brass works were erected in Birmingham about 1740 by the
Turner family. Birmingham is now the principal seat of the
brass industry of this country, and so rapid has been the develop-
ment within recent years, that in Birmingham alone prior to the
war more than 35,ooo persons (male and female) were employed
in the brass trade, the value of the metal consumed amounting
to four millions sterling.

Considerable impetus was given to the brass industry in the
early part of the eighteenth century by the introduction of
rolling mills, with the subsequent application of powerful stamping
machinery, in 1769, which enabled articles to be produced in sheet
metal more rapidly, with better finish and with less metal than
by the process of casting hitherto exclusively employed.

Among the more important factors that have contributed to
the enormous development of the zinc industry in more modern
times must be mentioned the introduction of gas fittings, in the
early part of the nineteenth century ; the use of brass tubes in
locomotives and marine engines ; the introduction of yellow
metal sheathing ; the extended uses of brass for engineer's work,
and for water fittings, &c. ; and more recently the very extensive
employment of the metal for electrical fittings.

174

INDUSTRIAL ZINC ALLOYS

Until the middle of last century, brass was exclusively made
by the old process of " cementation," in which metallic copper
was heated in crucibles in contact with calamine (zinc ore) and
carbon, whereby zinc was liberated and combined with the copper
to form the alloy known as " calamine brass." This ancient
process was superseded by the direct preparation of brass which
is now exclusively employed. This is effected by melting together
a mixture of copper and zinc, either in crucibles, or when very
heavy castings are required in a reverberatory furnace.

When prepared in crucibles the zinc is added to the copper
immediately after the latter is completely melted, the ingots
of copper having been heated to redness prior to their intro-
duction into the pots. In making castings, and in the remelting
of brass, there is always a considerable loss of zinc through
volatilisation, for which allowance must be made when arranging
the mixture.

The clay or graphite crucibles usually hold about 90 Ib. of
metal, but much larger pots are sometimes employed. The
crucibles are heated in small wind furnaces burning coke as
fuel, or in furnaces heated by gas or oil.

Zinc and copper alloy in all proportions, the resulting products
being of uniform composition throughout, as the metals do not
segregate. The colour and properties of the alloys vary with the
relative proportions of the metals. When the alloys are of a
decidedly yellow colour they are known industrially by the
general term " brass," although many special names have
been introduced by different makers to represent one and the
same alloy, thus giving rise to considerable confusion.

The term white brass is given to alloys in which zinc pre-
dominates, giving a white alloy. As a result of the work carried
out by modern methods of research, our knowledge of the consti-
tution of alloys of the zinc-copper series has advanced consider-
ably of late years. The constitution of alloys rich in zinc is
very complex, but these alloys are of little industrial value ; on
the other hand, the constitution of the alloys rich in copper
which constitute the brasses proper is comparatively simple. With
a few exceptions the zinc-copper alloys of industrial importance
may be said to contain from 50 to 70 per cent, of copper, and
within this range there are three constituents or phases, which
are respectively designated by the Greek letters a, /?,
and y.

THE ZINC INDUSTRY

Research has shown that in certain mixtures of metals there
is obtained one or more classes of crystal formation, dependirg
on the mutual solubility of the two metals. Thus iron and nickel
dissolve in one another in all proportions and give only one type
of crystals, no matter what the proportions. On the other hand,
zinc and copper are not mutually soluble in all proportions.
Starting with pure copper and adding zinc, the limit of solu-
bility is reached with 36 per cent, of the latter metal. Up to
this point only a-crystals are observed under the microscope,
beyond it ^-crystals appear with the a-crystals, and later
•y-crystals appear. The Alpha-constituent consists of a solid
solution of zinc in copper, the maximum content of zinc being
as stated, about 36 per cent, at 400° C. The Gamma-phase was
regarded by Shepherd as a solid solution, but as the result
of more recent research there is evidence to show that the
Gamma-phase contains a definite compound, Cu2Zn3, con-
taining about 40 per cent, of copper. The Beta-constituent
contains about 52 per cent, of copper and has the pro-
perties of a solid solution. According to Carpenter,1 however,
the so-called Beta-constituent splits up into an intimate mixture
of Alpha and Gamma on cooling from a critical temperature of
470° C. On heating above this temperature the reverse change
takes place. This critical temperature is found in all alloys
containing from 60 per cent, of zinc down to 28 per cent., and
probably less.

The Alpha-phase is relatively soft and ductile, and the Beta-
phase is harder and less ductile, while the Gamma-phase is still
harder and very brittle, and can be readily powdered in a mortar.
As the Gamma constituent is very brittle, the fact that the stable
phase above 470° C. is Beta, and below this temperature Alpha
plus Gamma, has an important bearing on the cause of the
brittleness and decay of many brasses in engineering work
(Carpenter)

The brasses containing more than 64 per cent, of copper
consist of a single homogeneous solid solution, while those con-
taining from 55 to 64 per cent, of copper are composed of two
constituents, each of which is a solid solution. Rapid cooling
from a suitably high temperature is capable of profoundly
modifying the structure and constitution, and consequently the
properties, of the zinc-copper alloys.

1 Journal of the Institute of Metals, 1911. i, vol. v, p. 127.

176

INDUSTRIAL ZINC ALLOYS

The constitution of the chief commercial brasses has been
classified by Hudson1 as follows : —

Copper per cent.

Nature of Constituent.

100-71
71-64

Consists entirely of Alpha-phase at all temperatures.
Alpha-phase below 400° C., Alpha plus Beta above.

64-63 j Alpha plus Beta at all temperatures.

Alpha plus Beta at low temperatures, Beta only at
some higher temperature.

53*1-51
51-40

Consists entirely of Beta at all temperatures.
Beta plus Gamma at low temperatures, Beta only
at higher temperature.

It will be noted that the proportion of the Beta-constituent
increases as the temperature rises, and this fact has important
bearings on the heat treatment of brasses. As shown by Charpy,
the effect of adding zinc to copper is to increase the tenacity and
to diminish the ductility.

With more than 40 per cent, of zinc, however, the tenacity
very rapidly decreases, whereas the ductility is diminished after
the addition of 30 per cent, of zinc.

Consequently, for ductile brasses the limit of zinc is usually
about 30 per cent., and in cases where a combination of ductility
and strength is required, as with brass for cold-drawn tubes, or
for cartridge cases, an alloy of about 70 per cent, of copper and
30 per cent, of zinc is preferred.

The industrial brasses may be conveniently considered under
three heads, viz. : (i) Cast brass, (2) low brass (i.e., low copper-
content) for hot rolling, and (3) high brass (i.e., high copper-
content) for cold rolling.

(1) Cast brass is very .variable in composition, but with the
exception of a few alloys rich in copper used in the manufacture
of cheap jewellery, &c., the usual composition of cast brass is
about 66 per cent, of copper and 34 per cent, of zinc, which is
known as English standard brass. It casts well, and is capable
of being rolled and hammered and even drawn into wire if so
required.

(2) Low brasses suitable for hot rolling contain from 55 to
63 per cent, of copper. The commonest of these yellow brasses
is that known as Muntz metal, patented by G. F. Muntz in 1832,

1 Journal of the Society of Chemical Industry, 1906, vol. xxv, p. 503.

177 N

THE ZINC INDUSTRY

and consisting of 60 per cent, of copper and 40 per cent, of zinc.
Although Muntz metal was originally introduced for sheathing
wooden ships, it is now chiefly used, either under the name of
Muntz metal or " yellow brass," for the cheaper varieties of
brass tube, wire and sheet.

Muntz metal is hardened by quenching, and the explanation
of this is readily seen from its structure. With increasing
temperature the Alpha-constituent is dissolved by the harder
Beta-constituent until, at 720° C., the alloy containing 60 per
cent, of copper .consists entirely of the Beta-constituent. If,
now, the alloy is quenched from this temperature the separation
of the Alpha-constituent is hindered, and the alloy will be found
to be stronger but less ductile than before.1

(3) High brasses, suitable for cold rolling, usually contain more
than 60 per cent, of copper. Whereas these alloys are readily
workable in the cold, they are quite brittle when hot, and, there-
fore, cannot be subjected to hot working. The best alloy of this
class is the brass used for tubes and wire drawing, which contains
70 per cent, of copper and 30 per cent, of zinc. This alloy
possesses the maximum elongation of the copper-zinc series
combined with a considerable degree of strength. On this
account it is used for the production of cartridge cases, alike for
rifle, machine-gun and the lighter types of artillery, and is fre-
quently referred to as " Cartridge " brass.

As it is subject to the severest of treatment, cartridge brass
requires that both the copper and zinc shall be as pure as
possible, 99*8 per cent, of zinc being a minimum, with o-i per
cent, of lead and o-i per cent, of iron as maxima.

The annealing of brass is carried out in reverberatory furnaces,
the temperature employed varying with the composition of the
brass. In the case of cartridge brass, the maximum effect of
annealing is reached at 600° C., whilst there is a very marked
softening of the alloy at 420° C.

Industrial brass is capable of withstanding very drastic treat-
ment, and in addition to rolling, drawing, stamping and spinning,
it is capable of being extruded or forced through dies at tempera-
tures somewhat below the melting point of the alloy. Great
advances have been made within the last few years in the extru-
sion of brass, and complicated sections which it would be im-
possible, to produce by rolling are now regularly manufactured by
1 " Alloys," E. F. Law, London, 2nd edition, 1914, p. 179.

178

INDUSTRIAL ZINC ALLOYS

this process (Law). The alloys used for this purpose usually
contain about 40 per cent, of zinc.

Brasses containing Iron. — The addition of iron to brass, first
suggested by Kier in 1779, imparts special hardness, toughness,
tenacity and wearing properties, whilst the alloy can be rolled
either hot or cold. In more modern times brasses containing
iron as an essential constituent have been introduced under
special names, such as " Sterro-metal," or " Gedge's alloy,"
" Aich's metal " and " Delta metal," which may be taken as
representative of the class.

These alloys, which are now largely used, consist essentially
of yellow brass, containing from 55 to 60 per cent, of copper
and 38 to 41 per cent, of zinc, with the addition of iron, which
varies from 1-5 to 4-5 per cent. In addition to iron, small
quantities of other metals are frequently added.

Sterro-metal contains 60 per cent, of copper, 38 per cent, of
zinc, and 1-5 to 2 per cent, of iron, and Aich's metal is practically
the same, although various analyses show that the percentage
of iron present varies within somewhat wide limits, and tin is
sometimes present. Sterro-metal can be made very hard and
dense by suitable mechanical treatment, which has as great an
influence in modifying its properties as its chemical composition.
In rolling or hammering this alloy when hot, special care is
requisite in regulating the temperature to which it is raised, as
it becomes brittle when overheated, and cracks under the hammer
or between the rolls.

Delta metal, introduced by Alexander Dick in 1883, varies
in composition, an average composition consisting of approxi-
mately copper 55 per cent., zinc 42 per cent., with i to 2 per cent,
of iron. In some cases small amounts of manganese, aluminium,
tin or lead are added to the alloy to impart special properties to
it.

Delta metal is stronger, harder and tougher than brass. It is
easily cast, forged or stamped, and is capable of beirg rolled hct
and drawn cold. In addition, it has a much greater power cf
resisting corrosion than ordinary brass, which enables it to te
used for many purposes where such brass is inadmissible, mere
especially for shipbuilding, marine engineering and sanitary we rk.
The maximum stress of Delta metal varies frem 27-8 to 35-4 tens
per square inch, according to the treatment to \vhich it has heen
subjected. The constitution of the ircn brasses dees ret appear

179 N 2

THE ZINC INDUSTRY

to have been sufficiently investigated ; when present in small
amounts the iron appears to enter into the alloy as a solid solution
and does not form definite chemical compounds (Law). When
more than about 2 per cent, of iron is present, the iron and zinc
would seem to combine. Formerly the iron was added to these
alloys in the form of a copper-iron alloy, but this was not found
to be entirely satisfactory, the metals in all probability not
being properly alloyed. Dick, when he patented Delta metal,
suggested the introduction of the iron in the form of an alloy of
iron and zinc, which can be obtained of reliable composition,
and is also relatively cheap as a by-product from the galvanising
process. Since that time iron-zinc alloys have been largely used.
The preparation of iron-zinc alloys for this purpose is dealt with
subsequently.

Brasses containing Lead.— A small addition of lead is beneficial
ia brasses intended for turning, the best alloy, and that which
is most commonly used, containing about 60 per cent, of copper,
38 per cent, of zinc, and 2 per cent, of lead ; it is sometimes
termed " clock brass." The lead is usually added after the zinc,
and while the crucible is still in the fire, the temperature being
kept as low as possible. Lead does not alloy with brass, but
separates out in the form of globules and films between the
crystals of the brass, a condition which necessarily weakens the
metal, so that the addition of lead is only permissible where
strength is of secondary importance. The fracture of brass
containing lead is distinctly grey in colour, owing to the fact that
the line of fracture passes through the lead.

The beneficial effect of lead in brasses intended for turning was
known long before the nature of its influence was understood.
Ordinary brass is difficult to turn owing to the character of the
turnings, which are long and tenacious, and tend to foul the
tools ; a slow speed has also to be employed. On the other
hand, the presence of lead in a free state in the brass renders the
alloy less tenacious, and the turnings break off through the lines
of weakness caused by the lead, so that chips are produced instead
of spiral turnings. The lead also appears to act as a lubricant,
with the result that a much higher speed can be employed and a
better finish given to the work. Brass containing not more than
2 per cent, of lead can be rolled, but the alloy is rolled cold, on
account of its liability to crack if rolled hot.
- Brass containing Tin. — A small percentage of tin renders brass,

180

INDUSTRIAL ZINC ALLOYS

and more especially low brasses of the Muntz metal type, less
liable to corrosion by sea- water when in contact with gun-metal.
On this account brasses containing tin are employed in naval
construction, the alloys being known as " naval " brasses. They
contain approximately 62 per cent, of copper, 37 per cent, of
zinc and I per cent, of tin. The mechanical properties of brass
are not seriously affected by the addition of I per cent, of tin,
but beyond this amount there is a rapid increase in brittleness
and hardness, whilst with more than 2 per cent, the alloys lose
their useful properties.

Many of the more important of the copper-zinc alloys are those
containing about 60 per cent, or less of copper in which part of
the zinc is replaced by small quantities of one or more other
metals, such as those mentioned above. The number of such
special brasses is now increased by the so-called vanadium
bronzes, in which cupro-vanadium is used as one of the in-
gredients. The actual effect of vanadium in alloys does not
appear to be very great.

Alloys of Zinc and Iron. — With iron zinc forms a series of
alloys which are generally white, hard and brittle. When the
iron does not exceed about 5 per cent, the alloys are less crystalline
and darker in colour than pure zinc ; such alloys are produced
in the process of galvanising, and are known as " hard zinc."
The alloys become greyer, harder and more brittle as the iron
content is increased. The alloy obtained by saturating zinc
near to its temperature of volatilisation with iron is not attracted
by a magnet ; it does not rust, nor give sparks by friction or
blows. It is dense in structure, but is only semi-metallic in
fracture, and contains about 22 per cent, of iron.

The zinc-iron alloys have a somewhat important application
in the preparation of the special yellow brasses, such as Delta
metal, which contain from 1-5 to 4-5 per cent, of iron, and to
which reference has been previously made.

The necessary zinc-iron alloy is prepared commercially either
(i) by direct union of the constituent metals, or (2) by the treat-
ment of hard zinc from galvanising. The alloys actually used
in practice generally contain from 7 to nearly 30 per cent, of
metallic iron.

The production of the zinc-iron alloys by direct fusion of the
metals is difficult owing to the high melting point of iron and
the volatile character of zinc. When prepared by this method,

181

THE ZINC INDUSTRY

clean iron wire, or sheet, is added to a bath of molten zinc heated
to near its boiling point. The union of the metals is facilitated
by the addition of a little charcoal and some solid ammonium
chloride. This method of preparation is usually accompanied
by a considerable loss of zinc.

Alloys rich in iron are usually obtained commercially by
liquating the hard zinc from galvanising works to remove part
of the zinc, and then strongly heating the residue, which is rich
in iron, in a closed crucible.

The excess of zinc is thus volatilised, leaving a zinc-iron alloy
in which the content of iron increases with an increase in the
temperature employed.

Nickel Silver or German Silver. — The white alloys manufactured
under these names consist essentially of nickel, copper and zinc.
An alloy composed of these three metals was known in early
times in China, and was exported to Europe in the eighteenth
century under the name of " pack-fong," or white copper.
Pack-fong seems to have been recognised as a triple alloy of
nickel-copper-zinc in 1776, when Engestrom published what
appears to have been the first analysis. The manufacture of a
white alloy composed of these metals was first started on a
commercial scale at Berlin, about the year 1824, and was subse-
quently exported to the United Kingdom as a cheap substitute
for silver, and it is probably owing .to this fact that the alloy
became known as " German silver."

Although alloys of nickel-copper-zinc are now usually known
in the trade under the general term of nickel silver, they probably
exist under a greater number of special names than any other
alloy, since different manufacturers employ fanciful names to
denote alloys containing different proportions of the constituent
metals which they consider best suited to produce an alloy of
good white colour and possessing satisfactory working qualities.
Thus Nevada silver, Virginia silver, Potosi silver, Silveroid,
Arguzoid, &c., may be given as examples.

The term nickel silver is somewhat misleading, as the alloy
does not contain silver. If a nomenclature which indicates
the true nature of the alloy be adopted, it would be described as
a zinc-cupro nickel, but it is probably more convenient to call
it a nickel brass, and this term is now usually adopted by research
workers on these alloys, although this name has to a certain extent
unfortunately become associated with the alloys of the copper-

182

INDUSTRIAL ZINC ALLOYS

nickel series containing no zinc and used for coinage pur-
poses.

The nickel silver alloys are now prepared largely as a basis
metal for electro-plating upon, and as a substitute for silver for
the manufacture of table forks, spoons, &c., the chief centres
of production being Sheffield and Birmingham.

In the form of wire they are used for electrical resistances.
The percentage of zinc in the industrial alloys varies from 20 to
35 per cent., and it is added as a substitute for the more expensive
metal nickel.

The various grades of nickel silver in general use in the United
Kingdom are known in trade circles as firsts, seconds, thirds and
fifths, which contain approximately the following percentages
of nickel : firsts, 20 per cent. ; seconds, 16 per cent. ; thirds,
12 per cent. ; fifths, 7 per cent. ; the content of copper appears
to vary between 56 and 59 per cent.

The alloy known as seconds is used by many firms as the basis
metal for electro-plate wares of best " A I " quality, although an
alloy of higher nickel content is preferred by others. The seconds
alloy is also largely used for the manufacture of best quality
nickel silver spoons, forks, &c., that are sold as such and not
plated.

The character of the silver deposit in relation to the composi-
tion of the basis metal has been studied by McWilliam and
Barclay,1 who conclude that when the proportion of nickel
exceeds 14 per cent, the silver is more liable to strip off irregularly
in actual use. It seems advisable, therefore, to avoid too high
a percentage of nickel in the basis metal for high-grade electro-
plate which has to endure rough usage. Although the alloys
poor in nickel are not so white and not so strong as the richer
alloys, the importance of the colour is not so great where there
is a heavy deposit of silver.

Owing to the high temperature required for the fusion of the
nickel, and the low melting point and ready oxidisability of
zinc, the preparation of nickel silvers is attended with a loss of
zinc, and special care is accordingly required in their production.
To overcome this difficulty the alloys are made by melting together
an alloy of copper and nickel (usually containing 50 per cent, of
each metal) and brass. The copper-nickel alloy has a lower
melting point than pure nickel, whilst the brass has a higher

1 Journal of the Institute of Metals, 1911, vol. v, p. 214.

183

THE ZINC INDUSTRY

melting point than zinc, and the melting points being thus more
nearly alike, the metals are more readily alloyed and the loss
of zinc by volatilisation is very materially reduced. This
method answers the double purpose of lessening the oxidation
of the zinc and of more readily producing a homogeneous
alloy. The alloys are made by melting the metals in the usual
way in graphite crucibles. Shortly before pouring the metal
a small quantity of manganese is usually added to ensure thorough
deoxidation of the alloy. The metal is cast in iron moulds similar
to those used in brass casting, but of different sizes.

In constitution the nickel-silver alloys, when cast, exhibit the
characteristic structure of quickly-cooled solid solutions, but, on
annealing, the crystallites undergo gradual absorption and are
replaced by the regular crystalline structure of simple metals
and homogeneous solid solutions, the addition of zinc to the
copper-nickel alloys not being attended with the formation of
compounds. They may be regarded either as brasses containing
nickel in solution, or as copper-nickel alloys containing zinc in
solution. The nickel silvers are greyer in colour and harder than
silver, and are capable of receiving a high polish ; their fracture
after casting is strongly crystalline, and the alloys require, in the
first instance, careful annealing before rolling or hammering ; but
after the crystalline character has been thus overcome, the metal
may be hammered, rolled or stamped into a variety of forms, whilst
some specimens possess considerable elasticity. The alloysof nickel,
zinc and copper become brittle when hot and are therefore always
rolled and drawn in the cold. Most of the alloys acquire a yellow
tarnish when exposed to the atmosphere, and in acid solutions,
such as vinegar, with access of air, they become coated with a
layer of verdigris, the rate of corrosion varying with the nickel
content of the alloy.

As in the case of most solid solutions, the alloys are softened
by annealing. This is effected in reverberatory furnaces so
constructed that a reducing atmosphere is, as far as possible,
maintained and oxidation kept at the minimum.

The temperature of annealing, which is of great importance,
has been found by recent research to vary from 700° C. to 900° C.,
according to the composition of the alloy, the higher temperature
being employed for the alloys of high zinc content. In works
practice annealing from twenty minutes to an hour, according
to the thickness of the sheets, at a temperature of about

184

INDUSTRIAL ZINC ALLOYS

750° C. is sufficient to render the metal soft enough for all pur-
poses.

For ornamental castings, nickel silver containing i or 2 per
cent, of tin is frequently used ; the presence of tin, however,
even in small quantity, makes the alloy decidedly yellow in
colour ; it also renders it brittle and unfit for rolling.

It has been frequently asserted that the brass and nickel silver
made in Germany and America, and imported into the United King-
dom prior to the war, is superior in working qualities to that pro-
duced in this country. Whilst there is undoubtedly some truth in
this assertion, it is well to bear in mind that this superiority of
product has only been attained by the use of pure metals, and the
application of scientific knowledge to the melting, casting and
heat treatment of the alloys, and also to scrupulous cleanliness in
all the processes through which the metal passes during manu-
facture. All these conditions for the production of high-grade
metal are equally available to British manufacturers, and it is
gratifying to know that within recent years many firms
have availed themselves of the rapid advancement of scientific
knowledge in the preparation and treatment of metals and alloys,
and are now producing metal equal in quality to any supplied
from foreign sources. On the other hand, it is unfortunately
true that there is still a considerable number of manufacturers
who appear to have inherited a certain conservatism, and a
tendency to cling to " rule of thumb " methods which may
produce alloys suitable for certain classes of work, but they
frequently fail to produce the high quality metal required to
withstand the severe mechanical treatment to which brass and
other non-ferrous alloys are now subjected in modern manu-
facturing processes, as in the production of cartridge cases.

Anti-friction Metals. — Zinc enters into the composition of a
number of so-called anti-friction alloys, or white metals, used
for bearings. Bearing linings of white metal are indispensable
for certain purposes, as they are soft and enable the axle to adapt
itself to the condition of the bearing and run with much less
friction than in the case of harder alloys. This tendency of white
metal to reduce friction has given rise to the term " anti-friction "
metal, which is now generally used for such alloys. One great
advantage of white metal alloys for this purpose is their low
melting point, which permits of a worn-out bearing being readily
melted out and replaced by a new one. The white metal is

185

THE ZINC INDUSTRY

generally melted in an ordinary ladle, and when the journal or
mandril is wiped dry and chalked, the molten metal is poured in.
Since the introduction of white-metal bearings an immense
number of so-called anti-friction metals have been placed upon
the market. The composition of these varies very considerably,
and they may contain copper, tin, zinc, antimony and lead ;
but seldom more than three of these metals are used in any one
alloy.

Whilst zinc in small proportions enters into the composition of
many anti-friction metals, the alloys in which the percentage of
zinc preponderates form a comparatively small class.

The composition of a number of white metals in which zinc is
the chief constituent is given in the table on p. 190.

From these figures it will be seen that the zinc content may
reach 90 per cent. The alloys of zinc, tin and antimony possess
a high compressive strength, and they are employed for bearings
of machinery, such as rock-breakers, where strength is of more
importance than perfect anti-frictional qualities.

Zinc Alloys for Die-casting. — Within recent years white metal
alloys containing zinc have found extensive application in the
production of die-casting or casting under pressure in steel moulds.
In this process the molten metal is forced into the die or mould
under a pressure of 100 to 400 Ib. per square inch, the pressure
being transmitted by a mechanically or hand-operated plunger,
actuated by compressed air or by centrifugal force. The alloys
used for the production of die-castings are generally white metals
of low melting points. The shrinkage of the alloys is an impor-
tant consideration, and involves special provision in making the
moulds. The shrinkage of zinc-base alloys, that is, those in
which zinc is the main constituent, is said to be about twice as
great as that of tin-base and lead-base alloys and about one-third
that of aluminium-base alloys. In a zinc-base alloy the shrinkage
is given as 0-004 inch per inch of dimension, thus indicating the
care required in making the dies, which are made of special alloy
machinery steel. The cost of the dies is very considerable, but
upwards of 100,000 duplicate castings, each accurate, may be
made from a properly constructed die, thus making the die-cost
per casting small.

In ordinary practice, die castings are made to dimensions of
plus or minus o-ooi inch to each inch of dimension.

The temperature of the dies and of the metal varies with the

186

INDUSTRIAL ZINC ALLOYS

different alloys used, so as to assist in controlling shrinkage.
The zinc-base alloys may contain zinc 50-80, tin 5-30, copper
2-20, aluminium 2-6, and antimony 1-5 per cent. A considerable
range of alloys is thus available in this series. The following
alloys may be given as representative of zinc-base white metal for
die-casting.1 Nos. i and 2 are stated to be suitable for ordinary
work in place of brass, No. 3 is harder and No. 4 harder still.

ZINC-BASE DIE-CASTING ALLOYS.

No. i.

No. 2.

No. 3.

No. 4.

Per cent.

Zinc

73-75

72-7 73-8

46-2

Tin

!4'75

ig-O I2-O

30-8

Copper

5-25

5-0 10-6

20-4

Aluminium

6-25

i-o 3-4

2-6

Lead

2-0 •

— .

Antimony

—

0-3 —

— '

Gas furnaces may be used for melting the metal, the pot being
covered to prevent oxidation, and the metal forced through a
tube and nozzle into the moulds.

The advantages of die-casting are low cost of production and
interchangeability, together with greater degree of accuracy —
in the case of small castings — than is possible by machinery.
The introduction of die-castings has done much to facilitate the
work of the foundry, as the process is adopted for making intricate
parts which would be expensive to cast in sand, to stamp in dies,
or to machine. The accuracy of die-castings having holes, screw
threads, teeth, &c., is as great as with ordinary machined parts.
Owing to technical difficulties the limit in weight of average die-
castings is given as 5 lb., although in special cases the weight may
be as high as n lb. Some of the uses of die-castings are as
bearing magneto parts, electric lighting and starting systems,
speedometer housings, &c., in automobile work, and as parts
in automatic machines, cash registers, &c.

Alloys of Aluminium and Zinc. — The importance of alloys of
aluminium and zinc has long been recognised, but it is only
within recent years that the price of aluminium has enabled its
alloys to be used on a large scale. Zinc forms solid solutions with
aluminium, and the alloys of these metals, either alone or more
1 Engineering, 1914, vol. xcvii, pp. 144-145.

187

THE ZINC INDUSTRY

often with small additions of other metals such as copper or
magnesium, are practically the only aluminium alloys of industrial
importance.

The alloys are largely used in connection with munitions of
war, as in certain parts of shells, in aeroplane construction, in
the motor industry and for many other purposes where strength
and lightness are desired.

Only the aluminium-zinc alloys containing less than 40 per
cent, of zinc are single homogeneous solid solutions, and they
are therefore the only ones of practical value. Those containing
up to 15 per cent, of zinc are soft enough to be rolled or drawn,
whereas beyond this amount the alloys are hard and more suitable
for castings, as they are easily worked. In practice the alloys
usually contain from 10 to 20 per cent, of zinc, with the addition
of a small quantity of copper. The properties of the aluminium-
zinc alloys have been investigated by Rosenhain and Archbutt,1
whose mechanical tests indicate that alloys containing frcm
15 to 25 per cent, of zinc (with or without addition of copper)
would be more serviceable than alloys containing less than
15 per cent, of zinc, which are much more widely used in present
practice. If dynamic as well as tensile tests be taken into con-
sideration, the alloy containing 20 per cent, of zinc appears to
be the most useful of the binary alloys. A characteristic feature of
the alloys is the very large effect produced upon them by hot work.

When the alloys are heated, the tensile strength falls rapidly,
but the hot alloys exhibit a considerable amount of ductility,
so that it is possible to roll into bars alloys which are brittle in
the cast state. The alloys containing respectively 25 and 20 per
cent, of zinc attain their maximum tensile strength when in the
form of rolled bar i J in. diam., the figures for the two alloys being :
ultimate stress, 27-5 and 22-64 tons per square inch ; yield point,
25 and 17*3 tons per square inch ; elongation on 2 in., 16*5 and
20-5 per cent, respectively. The alloys, with and without
addition of copper, differ from most non-ferrous alloys in that
in the rolled condition they exhibit a definite and well-marked
yield point. All the alloys containing from 10 to 30 per cent, of
zinc are very easily machined. Corrosion tests in sea-water
showed that the loss of weight increases with increasing zinc
content. The rapid corrosion (especially in moist air) frequently
observed with commercial aluminium-zinc alloys is attributed
1 Tenth Report to the Alloys Research Committee, Inst. Mech. Eng., 1912.

188

INDUSTRIAL ZINC ALLOYS

to the presence of impurities derived from the spelter employed
in their production.

The alloys are now very generally melted by means of coal-
gas as a fuel. Melting is performed either in graphite crucibles
or very commonly in cast iron pots, which are preferably pro-
tected by a wash of inert material.

Miscellaneous Zinc Alloys.- — The Biddery ware manufactured
at Bidar in India usually contains about 90 per cent, of zinc
together with copper, lead, and tin in different proportions.
Two analyses of Biddery metal are given in the table on p. 190.

Zinc alloys readily with silver, the alloys rich in silver presenting
some resemblances to the corresponding silver-copper alloys,
although somewhat whiter in colour. They are malleable and
ductile and take a high polish.

Silver-zinc alloys have long been used by native silversmiths in
India for the production of silver wares. Fcr this purpose the
silver is usually alloyed with about 10 per cent, of zinc.

Zinc in small proportions also enters into the composition of
a number of important industrial alloys.

The addition of a small quantity of zinc to certain alloys
increases their wearing power, and for this reason it is added to
the bronze used for coinage, which contains I per cent, of zinc,
4 per cent, of tin and 95 per cent, of copper. This alloy was
first used in England in 1861.

A standard Admiralty bronze consists of 88 per cent, of copper,
10 per cent, of tin and 2 per cent, of zinc, whilst in some alloys
of this class the percentage of zinc reaches 10 or even 15 per
cent. Statuary bronze usually contains from 2 to 10 per cent,
of zinc. The alloys used for this purpose lie midway between the
bronzes and the brasses and usually contain a considerable
percentage of lead.

The addition of zinc renders the alloy more fluid and greatly
facilitates the operation of casting. Too much zinc, however,
has to be avoided or the metal will have a brassy colour, and will
not assume a pleasing " patina " on exposure to the atmosphere.

The class of alloys known under the name of Britannia metal,
consisting of tin and antimony together with small quantities of
other metals, not infrequently contains zinc.

The percentage of zinc is, however, usually under 5 per cent.,
as it increases the hardness and brittleness of the alloy, and is
therefore not a desirable constituent if present in large amounts.

THE ZINC INDUSTRY

The composition of typical industrial alloys in which zinc is
an important constituent is shown in the accompanying table.

Typical Zinc Alloys.1

Alloy.

Composition per cent.

Remarks.

i*\

Aluminium.

Anti-friction Metals—
Anti-friction metal .
Babbits' metal (so
called) ....
Bearing metal
„ hard .
Bearing metal medium
hard
Bearing metal . .
Lumen bearing metal
Special „
Vaucher's alloy .
Brasses —
Aluminium brass . .
Best yellow brass

Brass

,, to be machined
Cast brass (so called),
very variable .
Naval brass .
Ordinary brass
Aich's metal . .
Delta metal (average
composition)
Muntz metal . .
Parson's white "brass"
Sterro metal . .
Brazing solder
Bronzes —
Coinage bron ze
(British)
Gun metal . . .

Manganese bronze .
Parson's white bronze
White bronze . . .
•' German Silvers " (so
called)—
Firsts . . . , .
Seconds . .
Thirds . . . . i
Fourths . . . .
Fifths
Miscellaneous —
Admiralty metal .
Ashberry metal .
Biddery ware .

Motor alloy . . .
White button metal .

85 'o

69-0
8'o

2'0

6-0
20*0
85-0
82-0
75 'o

38 o
30-0

S'o
2g'o

38-0

43-0
37'°
33 '3
38-0

36*0
40-0
30*0
55'5
50*0

I'O
2'0
1*0

42-0
38-5

29 'o

28-0
24-0
32'0

35 'o
36'o

28-5

I'O

84-3
93 '4

lO'O

8o'o

S'o

4'o
82*0
82*0

67-5
76 'o

lO'O
I2'C

60 'o

70'0

94 '5
70*0

60 'o

57-o
62 'o
66-6
6o'o

60 -o
60 'o
S'o
42-0
50-0

95 'o
88-0
86-0

54'5

2*5

4'5

56-0
62*0
56-0
55 'o
57 'o

i '5
2*0
11-4
3'5

2'0
20 0

19-0

lO'O

i6'o

21*5

3'o

S'o

...

lO'O

3'o

...

For locomotive axles.

Daimler motor-bus bearings.
For journal lining.

Sheet, wire, tubes, cartridges,
&c.
High-pressure turbine blades.
Condenser tubes. Admiralty
specification.

Admiralty specification.
Wires, sheets, &c.

Sheafhing.

Admiralty No. i.
Admiralty No. 2A to resist
high pressure,
o's Mn (composition varies).

For work under water.
Other metals 3 per cent.
Manufactured in India.

Light alloy for motoi-car
work.

I'O

S'o
6'o

2'0

iS'o

4 '5

2 '5

o'S

I'O

2'0
I'O

2'O

65*0

I'O

...

lO'O

13-0

05 'o

o'S

i '5

I 'O

°'5
o'S

...

i6'o

...

70 'o
8o'o
i'4

10 '0

7-0

'.'.'.

...

2-9
3 'i

14-0

...

S8'o

1 Compiled from tables in Law's Alloys, and other sources.
IQO

CHAPTER XII

COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS

OF the various compounds of zinc of commercial value zinc
oxide is by far the most important. It is largely used as a pigment
under the name of zinc white, and is valued for its permanency,
as it is not blackened by sulphuretted hydrogen like white lead,
for which it is a substitute. Although it lacks the body and
opacity of white lead, it has good covering power, and is non-
poisonous.

The zinc oxide of commerce is prepared either (i) direct from
zinc ore or (2) by the combustion of crude spelter. One of the
best known direct methods is the Wetherill process, which is
largely used in the United States, especially in New Jersey
and Pennsylvania. The ore treated is obtained from the mines of
Franklin Furnace, New Jersey, where it is crushed and con-
centrated, first by magnetic separators and then by jigs, giving
four products.1

The first, franklinite, consists mainly of oxides of zinc, iron
and manganese, with practically no injurious impurities.

This ore is worked by itself, making the best qualities of oxide.
The manganiferous residue remaining in the furnace after removal
of the zinc is treated in blast furnaces for the manufacture of
spiegeleisen. The second product contains about the same
amount of zinc as franklinite, but less iron and manganese, and
does not make quite so good an oxide. It is used, like franklinite,
for the manufacture of oxide, and the residues are thrown
away.

The third product is willemite, anhydrous zinc silicate, which
is used for the production of high-grade zinc. The fourth

1 Plant of the New Jersey Zinc Company. Oil, Paint, and Drug Report,
Nov. 2nd, 1914.

THE ZINC INDUSTRY

product consists of limestone tailings. The ore is shipped to
Palmerton, where a very extensive plant produces enormous
quantities of zinc oxide annually. The plant comprises 54 blocks
of furnaces with a total grate surface of about one-half acre.
Each furnace, known as a " Wetherill grate," consists of a
brick chamber with an arched roof and a flat grate, under which
is a closed ashpit. The ore is mixed with the quantity of
powdered anthracite necessary for its reduction, and then spread
over a layer of burning anthracite on the perforated grate of the
furnace, through which a low blast from a fan is forced, produc-
ing an underdraught. The zinc is volatilised and burned to
oxide by the excess of air above the charge. The zinc oxide
so produced and the products of combustion are drawn from
the furnace by large exhaust fans which draw them over to
the bag-rooms. These are provided, at the top, with distributing
pipes, from which hang muslin bags about 45 feet long and 6 feet
in circumference. The combustion gases pass out through the
bags and the oxide is collected in them. The bags are con-
nected with hoppers at the bottom, from which the finished
oxide is drawn to be taken to the packing room. The six bag-
rooms contain nearly 71 miles of bags, with a total surface of
51 J acres of muslin. The oxide is first sifted through wire screens,
and then fed into a packer which forces the oxide into barrels
or bags. The barrels are made at the works and contain 300 Ib.
of oxide each. For smaller quantities paper bags, containing 50
Ib. each, are used.

The Wetherill process is also carried out at Liege and other
places, but the ore used is generally zinc blende, which is first
converted to oxide by roasting.

Leclair's process of making zinc oxide by distilling and burning
metallic zinc, started between 1840 and 1850, is still in use in
Europe and also at the Florence works of the New Jersey Zinc
Company of Pennsylvania.

In the Silesian method, the spelter is heated to its boiling
point in retorts, and the vaporised metal is conveyed into
chambers through which air is kept in circulation, when the
metal burns, and the oxide, with more cr less metallic zinc,
is deposited in a series of condensing chambers. As the
crude spelter always contains some lead, which in this process
would be converted to oxide and impart a yellowish tint
to the zinc white, impairing its commercial value, a small quantity

192

COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS

of gas containing carbon dioxide is introduced into the retort.
By this means the lead is converted into carbonate, which is
considerably heavier than the zinc white, and therefore settles
first in the condensers.

In Belgium, zinc white is also made by burning spelter in the
manner described, but the final product is purified by levigation.
The spelter used in Belgium contains up to 2 per cent, of lead,
but the purified product contains under 0-2 per cent, of lead,
with very small amounts of iron, and zinc oxide from 99*69 to

99*99 Per cent-

Commercial zinc oxide nearly always contains lead compounds
(carbonate or basic sulphate), the presence of which affects its
market value. It has been claimed that zinc white made direct
from the ore is a more durable pigment than that obtained by
burning spelter.

Zinc oxide is prepared for pharmaceutical purposes by pre-
cipitating a solution of zinc sulphate with sodium carbonate
and igniting the basic carbonate thus thrown down. Zinc oxide
is a pure white, amorphous powder, which when heated becomes
yellow, but again becomes white on cooling. When ignited at a
high temperature it shrinks and becomes hard and gritty. It is
infusible at all ordinary temperatures, but distinctly volatile at
a white heat. The oxide does not fuse in the oxy-hydrogen
flame, but, like lime, in these circumstances becomes intensely
incandescent ; for some time after being so heated it appears
phosphorescent in the dark.

The oxide prepared by burning the metal has a specific gravity
of 5-6. It is insoluble in water, and does not combine
directly with water to form the hydroxide. It dissolves in
acids, producing the different zinc salts.

Commercial zinc oxide is not infrequently adulterated with
barium sulphate (barytes) , which is cheap and blends well with
the oxide.

An impure zinc oxide, known as zinc grey, is obtained as a
by-product in the manufacture of zinc white. It is used as a
silver-grey paint, and, when made into a paste with wood oil,
as a cement for steam joints.

Lithopone. — The important zinc pigment known as lithopone,
or Orr's zinc white, was first produced by T. B. Orr in 1874
(English patent of Feb. 10). Theoretically it is a mixture in
molecular proportions of zinc sulphide and barium sulphate, but

193 o

THE ZINC INDUSTRY

the products on the market contain other substances as well.1
The advantages claimed for it are that it is not affected by
sulphides and has high covering power, and its disadvantages,
due to particular methods of manufacture, are that on exposure
to sunlight it often turns grey and becomes chalky. It is prepared
by mixing solutions containing equivalent quantities of barium
sulphide and zinc sulphate. As in the case of other white pig-
ments, purity of raw materials is essential, iron compounds being
very objectionable.

Barium sulphide is obtained by roasting ground barytes
(barium sulphate) with coal or other carbonaceous material in a
reducing atmosphere, either in a flat bedded reverberatory
furnace or in a rotary kiln of the Bruckner type. Lixiviation
of the product of the roasting gives a solution of sufficient purity
for the purpose.

For the zinc sulphate solution any zinc-bearing material may
be used. Spelter and dross, when treated with sulphuric acid,
leave little or no zinc in the insoluble residue, but zinc ashes
usually leave so much mud in the solution tanks that the unit
of zinc in this material is not so valuable. Iron and manganese
when present are usually removed by boiling with bleaching
powder. The two solutions in proportionate quantities are then
mixed to produce the mixed precipitate, which is filter-
pressed and dried. In some cases about 0-5 to i-o per cent, of
a mixture of freshly prepared magnesia and common salt is
added to the precipitate before filtration. The dried precipitate
is mixed with 3 per cent, of ammonium chloride, and the whole
heated to dull redness to give it body, which it lacks if not
sufficiently heated. Excessive heating converts some of the
zinc sulphide into oxide. Some oxide is always found in litho-
pone, but it should not exceed 2 per cent. ; it ranges, however,
in commercial samples from 0-5 per cent, to as much as 12 per
cent. After burning, the red-hot pigment is at once quenched
and ground fine, after which it is thoroughly washed, dried, dis-
integrated, usually in pebble mills, and then packed.

Ordinary lithopone contains about 29-5 per cent, of zinc
sulphide. A higher grade, containing from 45 per cent, to 48
per cent, of sulphide, is produced by replacing part of the barium
sulphide by sodium sulphide, and washing out the resulting

1 " Lithopone," H. S. Riederer, Journal of the Society of Chemical
Industry, 1909, vol. xxviii, p. 403.

194

COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS

sodium sulphate. Lower grades are also made by replacing part
of the zinc sulphate by sodium sulphate. When used for outside
painting, lithopone is frequently mixed with other pigments, so
as to prevent the darkening which takes place when it is exposed
to sunlight. Unlike ordinary zinc white, lithopone is free
from lead.

Lithopone is chiefly made in the United States, and the
quantity made has increased considerably within recent
years. The amount produced in the United States in 1912 was
24,220 short tons ; in 1913 the output was 29,685 short
tons.

Zinc-lead pigment, or leady zinc oxide, consists of a mixture of
zinc oxide and sulphate, lead oxide and sulphate, with some
sulphurous acid and water. Commercial samples contain lead
up to about 25 per cent. The output of this pigment has been
rapidly increasing. It is usually produced by the treatment of
zinc-lead concentrates, or residues containing these metals.

Zinc oxide also finds limited application in the glass industry
for the production of opal glass, and also in the preparation of
crystalline glazes for pottery and stoneware, as such glazes are
less liable to " craze " than lead glazes.

Zinc chloride, ZnQ2, is formed by the direct combination of
zinc with chlorine, or by the action of hydrochloric acid upon the
metal. The latter method is adopted for the production of zinc
chloride on a large scale. For this purpose scrap zinc is placed
in hydrochloric acid contained in a stone, cast iron or wooden
vessel. The solution so obtained is neutralised with sodium
carbonate, warmed to 40° or 50° C. and bleaching powder added
to precipitate iron and manganese. When the precipitate has
settled, the clear solution of zinc chloride is siphoned off and
boiled down in enamelled iron pots. The evaporation is continued
until the temperature of the liquor is 230° or 240° C., a little
potassium chlorate is added to oxidise any organic matter, and
some pure hydrochloric acid carefully poured into the hot solu-
tion to dissolve any basic salt. The mass is then allowed to
solidify, and while still warm is packed in iron drums of from
30 to 50 kilos, capacity, which are at once closed air-tight.

When the aqueous solution of zinc chloride is evaporated,
partial decomposition takes place, hydrochloric acid being evolved
and basic compounds precipitated, consisting of combinations
of the chloride and oxide. Hence, during the concentration of

195 O 2

THE ZINC INDUSTRY

the liquid in the preparation of zinc chloride, hydrochloric acid
is added to re-dissolve this compound.

The anhydrous chloride is a greyish-white, soft, waxy-looking
substance, which is readily fusible, melting at 262° C. to a clear,
mobile, highly refractive liquid ; at a higher temperature it
volatilises and distils without decomposition, with the produc-
tion of peculiarly irritating fumes. It deliquesces rapidly on
exposure to moist air, and is very soluble in water or alcohol,
its solution being powerfully caustic.

From a strong aqueous solution, deliquescent crystals are
deposited on evaporation, having the composition ZnCl2,H2O.

A concentrated solution attacks and dissolves vegetable fibre,
consequently it cannot be filtered through paper ; it should be
filtered through asbestos or glass wool. When a solution of
zinc chloride is electrolysed, chlorine is evolved and crystalline
zinc deposited.

Zinc chloride is extensively used as a preservative of timber,
and it acts as a powerful dehydrant. It is much used for railway
sleepers, either alone or in combination with creosote. American
railroad companies buy sleepers specified to contain J Ib. of zinc
chloride per cubic foot, equal to about 0-5 per cent, of zinc. The
textile industry absorbs considerable amounts, and it is used in
" mercerising " or giving the appearance of silk to cotton goods.

In dilute aqueous solution it is employed as an antiseptic,
acting as a powerful disinfectant and germicide.

Zinc chloride for medical purposes is usually cast in the form
of small rods or tablets. A paste made by moistening zinc
oxide with zinc chloride rapidly sets to a hard mass ; this
mixture, under the name of oxychloride of zinc, is employed
in dentistry as a filling or stopping for teeth. Many of the
oxychloride cements used for this purpose contain small
amounts of other ingredients, such as powdered glass or silica,
to confer greater hardness on the mass when set. Other zinc
compounds used as cements by dentists are oxy-phosphate and
oxy-sulphate. The former consists of zinc oxide mixed with
one of the forms of phosphoric acid ; and the latter is a mixture
of zinc oxide and calcined zinc sulphate made into a paste
with a solution of gum arabic. Compared with metal fillings
these cements usually lack hardness, but they are non-irritating
and set fairly rapidly. They are all more or less readily acted
upon by the fluids of the mouth.

196

COMMERCIAL COMPOUNDS OF ZINC: ZINC PIGMENTS

Zinc oxychlorides are also used as pigments.

Zinc Sulphate, or White Vitriol, known also as zinc vitriol,
is prepared on the large scale either by the action of sulphuric
acid on zinc or by the treatment of zinc sulphide ore (blende).
In the former case commercial zinc scrap or zinc waste is
dissolved in sulphuric acid, and the solution evaporated to the
crystallising point. When produced from ores containing blende,
these are carefully roasted to produce zinc sulphate, which is
extracted with water, and • the salt crystallised from its aqueous
solution by evaporation. It was obtained, on a manufacturing
scale, by this method as far back as the sixteenth century. The
water from zinc mines is frequently charged with zinc sulphate
which is extracted by crystallisation.

The salt crystallises with seven molecules of water in colourless
rhombic prisms, which on heating fuse readily in their water
of crystallisation. Commercial zinc vitriol is made to assume
the shape of a sugar-loaf by stirring the fused salt in wooden
troughs with wooden shovels until crystallisation takes place,
and subsequently pressing the mass into moulds.

In common with all the soluble salts of zinc, zinc sulphate has
an astringent taste, and is poisonous. It dissolves in less than
its own weight of water at the ordinary temperature. When
exposed to the air, the crystals slowly effloresce ; if heated
to 100° C. they lose six molecules of water, leaving the
monohydrated salt, ZnSO4,H2O. At ja. temperature of about
300° C. this is converted into the anhydrous compound, and at
a white heat it gives off sulphur dioxide and oxygen, leaving the
oxide.

Zinc sulphate is used as a mordant in calico printing, and is
employed as a clarifying agent and preservative in the manu-
facture of glue. In medicine it is employed as an astringent, and
a very weak solution forms a common eye lotion. It, however,
finds its greatest application in the manufacture of lithopone, to
which reference has already been made.

197

CHAPTER XIII

THE FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

THE question of the future supply of zinc in sufficient quantity
for the maintenance and development of the metal industries of
this country, without the importation of foreign metal, has been
brought into special prominence by the exceptional circumstances
arising out of the world-war. The conditions which gave rise to
the very serious position in which this country was placed at the
outbreak of war in regard to her zinc supplies have already
been referred to. It has been shown that during the past
few decades the zinc market was becoming increasingly a
German monopoly. The war has, however, fortunately brought
about the beginning of a new epoch in the development of this
important branch of non-ferrous metallurgy, and if certain
comprehensive schemes, which have recently been formulated,
for the treatment of Imperial zinc ores in the United Kingdom
come to fruition, the increase in zinc production may be con-
siderable.

The first essential in the development of any industry is a
regular and ample supply of raw material, and where this is
lacking progress is invariably retarded. Undoubtedly one of the
obstacles to the expansion of the British zinc industry in the past
lies in the fact that for many years the smelters have relied for
raw materials chiefly upon the rich ores which have been shipped
in comparatively small lots from foreign sources.

Before the war there was little difficulty in obtaining all the
ore required to sustain the comparatively small output of metal
hitherto produced in this country, the ore itself being moderate
in price, whilst freights were low. Now the cost has greatly in-
creased, and the expenses of ocean transport have advanced
enormously and are likely to remain high for some time to come.

108

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

In respect to ore supply the British zinc smelters have always
been at a disadvantage compared with Continental and American
smelters, both of whom have sufficient domestic supplies of ore
available to augment that obtained from foreign sources,
and to ensure a steady and plentiful supply of raw material.
If Great Britain is going to produce all the zinc needed for
home consumption, the pre-war output of metal will have to
be increased at least five-fold, and this entails a corresponding
increase in ore supply and the building of much new plant.

But, as already pointed out, the available supplies of the rich
calamine ores, upon which British smelters have relied so much
in the past, are steadily decreasing, and there is little doubt that
in the near future the whole of the zinc of commerce will have
to be smelted from zinc blende. In these circumstances it is
very important that the supplies of this ore within the Empire
should be utilised for the development of the Empire zinc in-
dustries, and not left to the exploitation of foreign concerns.

As it has not infrequently been asserted that the superior
acumen and metallurgical knowledge of the Germans enabled
them to obtain control of the Broken Hill concentrates and treat
them successfully, it may be well to state, on the authority of
Moulden,1 that although the Germans obtained control of a large
proportion of the huge output of Australian zinc concentrates,
they did not treat them except in relatively small quantities.
They utilised this control to make money, in which they were
most successful, passing the major part of the concentrates on to
the Belgian works for smelting. Of the total Australian output
Belgium smelted at least 75 per cent, and Germany only 14 per
cent. The Germans had placed themselves in a position to force
this on the Belgian works by acquiring at the outset a controlling
interest in a number of them.

In this connection it is well to remember that the export of
Empire raw material to foreign countries for the recovery of
the commercial products is most undesirable in the interests
of this country. Not only is the benefit in wages, skilled
employment and greater profits involved in the working up of
the raw material to a refined metal lost to this country, but the
art of producing the finished metal and its alloys, and the
control of it, pass into alien hands. In this way supplies of
indispensable metals, such as zinc, can only be obtained by paying
1 Moulden, op. cit., p. 528.
199

THE ZINC INDUSTRY

enhanced prices, or may be cut off altogether in times of urgent
need, as experience has unfortunately proved.

It may be well to repeat that the extensive deposits of zinc
ore at Broken Hill, New South Wales, afford an ample supply of
ore, sufficient to meet all the zinc requirements of the United
Kingdom for some years to come, and now that the difficulties
which at first attended the treatment of the ore have been
successfully overcome, there is every reason why this ore
should be smelted in preference to ores from foreign sources.
The importance of treating Broken Hill zinc concentrates within
the Empire, and more particularly in this country, becomes more
apparent on reviewing the situation as created by the war. The
effect of the outbreak of war on the zinc industry was felt more
quickly in Australia than in Great Britain. The mines, deprived
of the greater part of their market, had to curtail production very
considerably, and it is to their credit that, in order to minimise
hardships among their labouring population, they continued to
produce considerably more ore than they could for the time being
dispose of. Certain considerations bearing on the question of
the future markets for Broken Hill concentrates have been
enumerated as follows.1

(1) Australian legislation has been passed cancelling the
contracts for the sale of Australian ores to alien firms and
prohibiting them for the future, so that no zinc concentrates
will be henceforth shipped to Germany. The Australian mine-
owners will therefore have to find fresh markets for that
considerable proportion of their ore which previously went to
Germany or to the German smelters in Belgium.

(2) Germany, in spite of the length of time that her own ore
deposits have been worked, has still large reserves. She has
also considerable zinc-mining interests in China, and before the
war shipped zinc concentrates from that country. She will
not fail to develop her trade in this direction as far as she is able
to do so after the war, and will continue to be an important
producer of spelter.

(3) The United States zinc smelters will be formidable com-
petitors after the war so long as high prices are maintained. They
have used their large profits wisely in making their plants efficient
and up to date, and in accumulating large financial reserves.
Their present rate of production is sufficient for more than 70 per

1 H. C. H. Carpenter, Nature, 1916, vol. xcviii, p. 129.
200

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

cent, of the world's peace requirements before the war. They
will have considerable tonnages of the metal available
for export. They have very large ore supplies, not only of
" straight " zinc ores, but of the complex ores in which zinc blende
is associated with galena and other metallic sulphides, and which
now constitute an increasingly important source of spelter. It
is very unlikely, therefore — quite apart from the 10 per cent.
ad valorem tariff to which zinc ores imported into the United States
are liable — -that Australian zinc concentrates will find a market
in America.

(4) The Canadian Government is encouraging zinc extraction
by granting bounties on zinc produced in Canada from Canadian
ores. Australian concentrates are therefore not likely to enter
Canada to any great extent.

(5) The future of the Belgian industry is quite uncertain, but
it is much to be hoped that it will be re-established and the
smelting works rebuilt after the war, and in this case, as it will
depend largely on imported ores, there may be a renewal of the
contracts with the Broken Hill mine-owners.

(6) By virtue of the magnitude of its population, its transport
facilities, markets and the raw materials necessary for zinc
smelting — apart from the ore itself — Great Britain is the most
suitable country for the treatment of Broken Hill concentrates
exported from Australia. The future development of the British
zinc industry is largely dependent on the facilities that will be
afforded for their treatment, by the adaptation and enlarging of
existing works, and the erection of new works for the extraction
of the zinc and other metals, &c., by distillation, or by electrolytic
or other processes.

The Australian Government has dealt with the situation
created there, and a scheme has been drawn up affecting the
future of the zinc mining and smelting industry, and one in which
Australia and Great Britain are immediately concerned. It does
not appear probable that America will be able to compete in the
supply of spelter at a reasonable price on the English market
after the war.

A new company, known as the Zinc Producers' Association
Proprietary, Limited, has recently been formed to handle all
zinc concentrates produced within the Commonwealth. This
is the largest and most powerful metal combination in the
Southern Hemisphere, and one of the most important in the

201

THE ZINC INDUSTRY

world.1 The Commonwealth's annual output of zinc ores and
concentrates amounts to 450,000 tons, and the gross value of
metal is not less than £5,000,000. All the zinc-producing
companies of Australia are members. The Association will act
for all Australian producers of zinc ores who belong to it during
the next fifty years, on a co-operative basis, the companies under-
taking to have all their smelting done through it. One of the
fundamental principles is " equality of treatment " of all
members, irrespective of the tonnage of output. The Common-
wealth Government is represented on the board, thus safeguard-
ing the interests of the general community.

In spite of the Commonwealth Prime Minister's efforts in
England, the spelter question has not yet been definitely settled
so far as Great Britain is concerned. A contract has been
entered into for a large supply of zinc concentrates per annum
for Great Britain during the continuation of the war, with the
option of increasing the quantity. The British Government has
entered into a definite agreement for a term of ten years to
take a minimum of 100,000 tons of Australian concentrates at
satisfactory prices.

As to the remainder, arrangements have been suggested
whereby Australia will treat locally 40 per cent, of the whole
of the zinc concentrates produced in the Commonwealth.

The British Government has further contracted to take up to
45,000 tons per annum of spelter and electrolytic zinc produced
in Australia for a period of ten years. The post-war require-
ments of France, Belgium and the other Allies are being
considered.

In order to deal with some of the zinc concentrates reserved to
Australia under the scheme, a company, called the Australian
Electrolytic Zinc Company, has been formed, and will, it is
hoped, be successful.

Contracts for power have been arranged with the Tasmanian

Government ; technical experts have been engaged in America,

and the company promises to be one of the foremost industrial

concerns in the Commonwealth. Towards securing capital for

Australian zinc industries the Imperial Government undertakes

to advance a substantial sum at the same rate of interest as is

paid by the Imperial Government, if required, to finance

Australian zinc works until war restrictions are removed. ' The

1 Chamber of Commerce Journal, March, 1917.

202

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

Mount Lyell Company is embarking upon a new venture, and
promises to be a large producer of electrolytic zinc. The enlarge-
ment of the Port Pirie zinc distillery is receiving attention. Zinc
specialists have been engaged to undertake the modernisation
of the zinc distilling plants in Australia, and also to install and
work the electrolytic zinc processes. All the above provisions
will, however, only permit of the treatment of a portion of
the zinc concentrates which can be produced in Australia for
which concentrating plant is already in existence. What is to
become of the balance of the concentrates available for smelting
is uncertain, but Japan has already made offers for purchasing
considerable quantities.

With regard to the development of the British zinc industry
there has been much discussion ; it has been proposed to erect
large smelting works in this country under Government subsidy,
in addition to the extension of existing works, with a view to
largely increase the output and render this country less dependent
on foreign supplies. A special committee has been appointed
by the Secretary of State for the Colonies and the President of
the Board of Trade to elaborate a scheme. What is involved
in this proposition is best seen by reference to the figures repre-
senting the output and consumption of zinc in the United
Kingdom under normal conditions. From the few available
statistics it would appear that the maximum production of
spelter in this country in any year before the war was approxi-
mately 58,000 English tons, whereas the consumption was
approximately 200,000 tons, the difference between production
and consumption being 142,000 tons.

The actual production for 1913 was 58,298 tons, of which, as
previously stated, probably not more than 31,290 tons was
" primary " spelter, produced direct from ores, the balance of
27,008 tons being " secondary," or remelted metal from the
treatment of by-products, &c. Thus secondary zinc forms an
exceptionally abnormal proportion of the total British output.

Practically the whole of the primary spelter was produced
from imported ores, the metal produced from British ores being
comparatively insignificant and probably amounting to not more
than 2,500 tons.

The consumption of virgin zinc in 1913 was 203,302 tons, of
which no less than 145,004 tons was imported.

The actual consumption of spelter in 1913, after allowing for

203

THE ZINC INDUSTRY

imports of zinc wire and sheet, and that present in imported
brass, was 224,000 tons, but even this does not include the zinc
contained in zinc dust, zinc oxide, lithopone and salts of zinc
(chloride and sulphate), figures for the import of which are difficult
to obtain, but the quantities are by no means inconsiderable.

The imports of drawn and rolled zinc in 1913 were 18,768 tons.
With regard to these imports it is of interest to note that in
1913 Germany imported 313,269 tons of zinc ore, 57,641 tons of
spelter and 725 tons of drawn or rolled zinc, and exported in the
same year 44,731 tons, 109,606 tons, and 24,965 tons of these
materials respectively. It should be noted also that the British
statistics refer only to the United Kingdom, and take no account
of the imports of crude or manufactured zinc into Canada,
Australia, South Africa and India, which were large.

From the above figures it will be evident that in order to render
this country independent of foreign supplies of zinc it will be
necessary to smelt sufficient ore to produce annually at least
140,000 tons more spelter than has been produced in the past.

Apart from the provisions that have been made recently for
an adequate supply of zinc ore for British smelters there is very
little information available as to what steps are being taken to
increase the output of metal in this country. According to the
latent report of the Inspector of Alkali Works, extensive additions
were made to registered zinc works in 1916, but no new works
were added. In 1916 the Sulphide Corporation acquired the
smelting works of the Central Zinc Company at Seaton Carew,
and in 1917 they purchased the sulphuric acid works constructed
by that company for £52,000. These works utilised the
sulphurous gases coming from the zinc-roasting furnaces, The
smelting works are to be doubled, and when this is accom-
plished they are expected to be able to treat 30,000 tons of Broken
Hill concentrates yearly, equal to an annual output of zinc of
about 12,000 tons. This tonnage amounts to one-half the
Sulphide Corporation's output of zinc concentrates.

Considerable additions are also being made to the Swansea
Vale Spelter Works, the largest works in the Swansea district.
Good progress has been made with the extensions, which, when
completed, will give an output of 15,000 to 20,000 tons of spelter
per annum. Extensions are in progress, or completed, in other
works, and according to a recent estimate when all the new
plant is erected the total capacity of the British smelting

204

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

works will be about 78,000 tons of primary spelter, made up as
follows : *

Works. Capacity.

Swansea Vale . . . . . . . . 20,000 English tons.

English Crown Spelter . . . . 18,000

Vivians . . . . . . . . . . 10,000

Seaton Carew . . . . . . . . 10,000

Dillwyn . . . . . . . . . . 8,000

Williams Foster . . . . . . 6,000

Sundry lesser plants . . . . . . 6,000

Total . . . . . . 78,000 English tons.

This estimate is based on the theoretical capacity of the
respective plant extensions when finished ; the actual produc-
tion would naturally be lower. According to this estimate
the total production of zinc from ores will be approximately
50,000 tons more than the pre-war output of virgin metal, or,
including secondary zinc, an increase of nearly twice the pre-
war annual output.

To encourage the smelting of Broken Hill concentrates by
British smelters the Government, in connection with the British-
Australian scheme, has guaranteed the minimum price of £23
for ordinary spelter and £28 for high-grade spelter.

An agreement has also been reached between the spelter
producers in this country and the Ministry of Munitions on the
subject of new works. The producing companies are to be
allowed to deduct from their excess profits the difference between
the cost of new production during the war and before the war ;
they are also to receive from the Ministry of Munitions a
" reward " for extending their works, in that they will be allowed
to deduct from their excess profits, before taxation, 50 per
cent, of the pre-war cost of construction.

Before the war it was agreed by producers generally that it
did not pay to produce permanently under £22 per ton. With
existing methods and conditions of production, the cost for
some time to come must be considerably more.

In these circumstances it is considered by many that the

margin of profit is not sufficient to stimulate private enterprise.

In this connection it may be permitted to quote the opinion of

Mr. J. C. Moulden, who has had a wide experience in zinc smelting.

Compared with the production of other metals in common use,

he considers " that there is no branch of the metallurgical industry

1 Mining Journal, London, 1917, vol. cxvi, p. 66.

205

THE ZINC INDUSTRY

in which, considering the difficulties and risks involved, the
invested capital has been so ill-requited as that of zinc.
What profits there have been were made largely by the ore
and metal-dealing firms, and those who, in addition to smelting,
turned out rolled and stamped zinc together with lead and silver
from complex ores — and possibly also zinc oxide." That zinc
smelting can, however, be profitably undertaken, under favour-
able conditions, and by the utilisation of all the valuable by-
products, with good management and if equipped with labour-
saving appliances, is evident from the fact that the Continental
zinc-smelting companies have in recent pre-war days paid divi-
dends of 20 to 25 per cent, and over. Under the conditions
that obtain in this country it seems obvious that the Government
must undertake the cost of erecting new works if they want to
see the position much further advanced, and it is the uncertainty
of what they are going to do which makes an estimate of the
outlook for home production so much a matter of hypothesis,
and which prevents private capitalists from embarking. The
problem is obviously a very different one for the Government in
contrast to private enterprise. They have not merely to
consider the question from the point of view of the price of
spelter after the war. Beyond economic factors there is the
consideration of the public safety in view of possible restric-
tions on the necessary supplies of sulphuric acid and spelter.

Assuming that the above estimate of increased production is
substantially correct, it will be evident that something like another
100,000 tons of metal will be required to bring up the spelter
production to correspond with the pre-war consumption, and it
is to supply this extra output that the construction of smelting
works by the Government has been suggested. The erection of
smelting works at Avonmouth, capable of producing 24,000 tons
of zinc per annum from Australian ore, has been proposed, and
in this connection the Bristol City Council recently sanctioned the
preparation of schemes for extending the accommodation of the
Royal Edward Dock to meet the traffic incidental to the proposed
shipment of zinc concentrates from Australia. Negotiations for
the treatment of further quantities of these concentrates at
Widnes, and possibly elsewhere, are also in progress. But after
allowing for the carrying out of the present programme for the
expansion of the productive capacity of existing works, even in-
cluding the 24,000 tons per annum for the proposed new works at

206

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

Avonmouth, it would appear that the possible output will be only
about one-half the pre-war consumption. It is most unfortunate,
in the future interests of the zinc industry in this country, and
in the interests of the metal industries dependent on metallic
zinc as raw material of first importance, that the Government
has not, up to the present, taken any steps to begin the erection
of new zinc-smelting plant. Moreover, it cannot be too strongly
urged that the provision for increased zinc output so far suggested
is inadequate to meet the situation, and the erection of large
works would be one of the greatest factors in supplementing the
zinc deficiency, and would help to keep the production in our
own hands and remove our dependency on metal from foreign
sources.

In addition to the home output, there is the proposed spelter
production from Australia, which, as stated above, is to be
imported to the extent of 45,000 tons per annum, and which
would be of great assistance in making the total output approxi-
mately equal to the demand.

Climatic and labour conditions are, however, against any
large extension of zinc distilling in Australia, and up to the
present only the erection of small plant has been started there,
and for a long time to come no appreciable tonnage of metal can
be expected.

The Government has bought supplies of Broken Hill zinc
concentrates, and many tons have been shipped to this country,
but they are of no value to the country until they are turned into
metal. The erection of works to effect this with all possible
speed becomes imperative. It may be well to emphasise the
fact that the complete treatment of these concentrates involves
not only the production of zinc, they are also a potential source
of sulphuric acid, and of lead and silver, and for economic reasons
they should be worked to produce all these. The general method
of treating the concentrates is shown in the accompanying flow
sheet, (p. 208.)

To erect new zinc-smelting plant without proper provision for
the utilisation of so valuable a product as the sulphur would
undoubtedly be a serious mistake, and would greatly hinder the
future development of the British zinc industry which is so
urgently necessary, because it would not only waste a product of
considerable value to the chemical industries, but would also
deprive the zinc industry of a source of profit and increase the

207

FLOW SHEET SHOWING THE GENERAL METHOD OF TREATING AUSTRALIAN
ZINC CONCENTRATES.

Zinc Concentrates.

Roasting to expel
Sulphur.

Sulphur fumes.

Roasted Concen-
trates mixed with
Coal.

Sulphuric Acid
Works

Market.

Distillation.

N ,

Zinc Powder.

Spelter.

Furnace Residues
(containing Lead
and Silver.)

Sifted through
70-mesh Screen.

Market.

Concentrated
in jigs.

N ,

Packed in Drums
or Barrels.

Argentiferous
Lead Concentrate.

^ '

Market.

Lead Smelter.

b.ead ^k
ilver)

To Market.

208

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

difficulty of meeting foreign competition. It is just the fact that
this ore is a potential source of sulphuric acid which renders it
necessary for the bulk of the concentrates to be shipped from
Australia, where the market for acid is limited, to a country like
Great Britain, with nine times the population of Australia and
highly developed industries which can absorb the acid.

Probably one of the most difficult problems in connection with
the utilisation of the sulphur is to decide on the most suitable
location of the plant for roasting the ore. The Swansea district
is one of the most favourably situated places in the world for
the production of zinc and is the chief seat of the British industry,
but it does not follow that the roasting of the ore for acid should
necessarily be effected at the same place as the smelting of
the roasted material for the metals. As already pointed out, it
is not uncommon to find the roasting and the manufacture of
sulphuric acid carried on in one district and the roasted ore
smelted in another district where economic considerations render
this course desirable. In treating the Australian concentrates
in this country, therefore, it may be found, after a due con-
sideration of all the circumstances, to be more suitable to roast
the ore for acid at some centre connected with the chemical or
galvanising industries, and to treat the roasted ore for zinc and
its allied metals at Swansea or some other zinc-smelting centre,
or even to extract the zinc in the same locality as that in
which the sulphuric acid is made.

In adopting this latter course a considerable quantity of by-
products from galvanisers' works would be available in the
immediate proximity of the projected smelting works, and the
saving in freight alone on this material would probably be
considerable. A most important element in favour of a scheme
for the production of sulphuric acid from the roasting of concen-
trates is the keen interest shown by the leading manufacturers
of sulphuric acid, who have been longing for an opportunity
to adopt the Belgian blende roasting system in preference to the
roasting of pyrites, which have been advancing in price con-
siderably of late.

There is always an increasing demand for sulphuric acid in
this country, especially for non-arsenical acid, as produced from
zinc ores.

The whole question of the treatment of the Broken Hill zinc
concentrates is, in view of the commercial and military

209 P

THE ZINC INDUSTRY

value of zinc, of great importance, and the Government
authorities have rightly decided that the handling of what is
undoubtedly a great Imperial asset requires careful consideration.
At the same time, there seems to be no reason why that con-
sideration should be indefinitely deferred, and why, under proper
safeguards to retain the control of this asset of the Empire, the
treatment of the ore for its zinc and other valuable constituents
should not be proceeded with without further delay, so that the
country may be relieved of the necessity of importing spelter.
The shortage of domestic zinc is bound to continue unless works
are built capable of dealing with the zinc concentrates from
Broken Hill. The war may yet last a long time, and it will
scarcely be possible to hold up all trade and development
questions until peace arrives.

The establishment in this country of a zinc-smelting industry
on a scale commensurate with its needs is most urgently required.

There is no reason, if there is a proper application of organising
ability, technical knowledge, perseverance and resourcefulness,
why success should not be achieved.

We have in the country metallurgists with knowledge and
experience of the very best Continental zinc-smelting plants and
methods ; we have the raw materials in ample quantity in the
Empire ; we have the demand for the metal, but we have not yet
availed ourselves of these.

As Professor H. C. H. Carpenter 1 has well said, " the establish-
ment in this country of a zinc industry on a scale commensurate
with its needs would be an industrial victory of the first magnitude
and it would remove a peril in which this country was placed
by the outbreak of war, a peril which has been all too imperfectly
realised, and should never be allowed to recur."

The urgent need is to make provision for the reconstruction
that must follow on the declaration of peace, and in that recon-
struction the development of the zinc industry holds an important
place. There can be no doubt that further to neglect to respond
to the urgent demands for a largely augmented output of zinc
in this country will very seriously interfere with the progress of
the non-ferrous metal industries, which have hitherto played so
important a part in the industrial development, not only of this
country, but of the British Empire, and are destined to be of
much greater importance in the near future.

1 Nature, 1916, vol. xcviii, p. 131.
210

FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN

The question as to what is going to be the future of the zinc
industry in this country is one which has been exercising the
mind of those who have the welfare of this industry at heart ever
since the lamentable and dangerous situation at the outbreak of
war was revealed. One cannot refrain from comparing the long
delay in dealing with the question of the future development of
the British zinc industry with the very expeditious manner in
which the Royal Ontario Nickel Commission, appointed by the
Ontario Government in September, 1915, dealt with the question
of the nickel industry. Although many countries were visited,
the Commissioners have, after a lapse of only eighteen months,
presented their valuable and exhaustive report, which deals very
fully with the nickel question, especially in relation to industry
and trade, and will form a standard work of reference on nickel
for many years to come. As the result of the recommendations
of the Commissioners, extensive works are now being erected in
Ontario for the treatment of the large quantities of ore found in
the district, which have hitherto been mainly treated in the
United States.

2ir P 2

BIBLIOGRAPHY

The Metallurgy of Zinc.

John Percy. " Metallurgy of Copper, Zinc and Brass/' London,

1861.
W. R. Ingalls. " Production and Properties of Zinc," New York,

1902.
L. von Wiese. " Beitrage zur Geschichte der Wissenschaft-

lichen Entwicklung der Roh-Zink Fabrikation," Jena,

1903.

W. R. Ingalls. " The MetaUurgy of Zinc," New York, 1903.
Lodin. " Metallurgie du Zinc/' Paris, 1905.
O. W. Brown and W. F. Oesterle. " The Electric Smelting of

Zinc," Transactions of the American Electrochemical

Society, 1905, vol. viii, p. 171.
W. R. Ingalls. " Lead and Zinc in the United States/1 New

York, 1908.

" The Metallurgy of Zinc and Cadmium," 1908.

J. S. G. Primrose. " Notes on the Production of Pure Spelter,"
Journal of the Institute of Metals, 1909, vol. ii, pp.
231-248.

J. C. Smith. " Oxide of Zinc : Its Nature, Properties and Uses,"
London, 1909.

" Official History of Vieille Montagne," 1837-1910.

C. O. Bannister. " Carbonaceous Filters in the Smelting of

Zinc," Journal of the Institute of Metals, 1910, vol. iii,

pp. 213-231.
H. L. Sulman. Presidential Address (contains references to the

Zinc Industry), Transactions of the Institution of

Mining and Metallurgy, 1910, vol. xx.
213

BIBLIOGRAPHY

F. W. Harbord. " The Electric Smelting of Zinc Ores at Troll-

hattan," Official Report, 1911. Also Engineering and

Mining Journal, New York, 1912, p. 314.
W. McA. Johnson. "The Art of Electric Zinc Smelting,"

Transactions of the American Electrochemical Society,

1913, vol. xxiv, p. 191.

Liebig. " Zink und Cadmium," Leipzig, 1913.
C. Schnabel. " Handbook of Metallurgy," vol. ii, containing

Zinc, Cadmium, Mercury, etc. Translated from German

by H. Louis, 1916.
H. F. Moore. " An Investigation of the Strength of Rolled

Zinc," Bulletin, No. 52, 1913, University of Illinois

Engineering Experiment Station. (Supplied by Chapman

and Hall, London.)
C. V. Lordier. " Review of Electric Furnace Methods of Zinc

Smelting," Metaux et Alliages, 1914, vol. vii, No. 12,

p.i.

" The Metallurgy of Zinc," Transactions of the American

Institute of Mining Engineers, 1914.

R. Sylvany. " Review of the Electro-Metallurgy of Zinc,"
Mttaux et Alliages, 1914, vol. vii, No. 9, p. 2.

J. N. Pring and U. C. Tain ton. " The Electro-Deposition of
Zinc," Transactions of the Chemical Society, 1914,
vol. cv, p. 710.

J. W. Richards. " The Electrolytic Refining of Zinc," Transac-
tions of the American Electrochemical Society, 1914,
vol. xxv, p. 281.

W. Me. A. Johnson. " The Commercial Aspect of Electric
Zinc-Lead Smelting," Transactions of the Canadian
Mining Institute, 1914, vol. xvii, pp. 107-129.

W. Gowland. " The Metallurgy of the Non-Ferrous Metals,"
London, ist edn., 1914 ; 2nd edn., 1917.

G. C. Stone. " Spelter : Its Manufacture and Properties,"

Transactions of the American Institute of Mining
Engineers, 1915, vol. ix.

W. R. Ingalls. " The Economics of Zinc Metallurgy," Paper
before the International Engineering Congress, San
Francisco, 1915.

" The Occurrence and Utilisation of Zinc Ores," Part I,

Bulletin of the Imperial Institute, London, 1915,
vol. xiii, pp. 611-634.

214

BIBLIOGRAPHY

E. H. Leslie. " Zinc-Smelting in the Middle West." (Reprinted

from Mining Magazine}. London, 1915. (Gives full

technical details of modern zinc-smelting in Illinois and

Oklahoma, U.S. America.)
W. R. Ingalls. " The Occurrence and Utilisation of Zinc Ores/'

Part II, Bulletin of the Imperial Institute, London,

1916, vol. xiv, pp. 44-80.
Rigg and Morse. " The Effects of the Common Impurities in

Spelter upon Slush Castings," Journal of the American

Institute of Metals, 1915.
— " Pure Spelter Manufacture in the Electric Furnace,"

Journal of the Society of Chemical Industry, 191 6>

vol. xxxv, p. 1263.

C. E. Siebenthal. " The American Zinc Industry," Paper before

the American Mining Congress, November, 1916.

D. A. Lyon, O. C. Ralston and J. F. Cullen. " The Hydro-

metallurgy of Zinc in 1915," Metallurgical and Chemical
Engineering, 1916, vol. xiv, pp. 30-32.

A. Stansfield. " Electric Furnaces as Applied to Non-Ferrous
Metallurgy " (includes references to the electric smelting
of zinc ores), Journal of the Institute of Metals, 1916,
vol. xv, pp. 277-304.

J. Gilbert. " Costs and Profits of an Up-to-date Spelter Works,"
The Mining Journal, London, 1916, vol. cxiv, pp. 480—
481, 496-498.

J. C. Moulden. " Zinc: Its Production and Industrial Applica-
tions " (Peter Le Neve Foster Prize Essay), Journal of
the Royal Society of Arts, London, 1916, vol. Ixiv, pp.

495-513 and 5I7-53I-

W. R. Ingalls. " Electrolytic Zinc," Transactions of the
American Electrochemical Society, 1916, vol. xxix,
p. 347. Also, with additional notes, The Engineering and
Mining Journal, New York, 1916, vol. ci, pp. 425-428.

E. A. Smith. " The Development of the Spelter Industry,"

• Journal of the Institute of Metals, 1916, vol. xvi,

pp. 118-195.

W. R. Ingalls. " Cadmium in Spelter," Journal of the Institute
of Metals, 1916, vol. xvi, pp. 196-204.

• " Comments and Speculations on the Metallurgy of Zinc,"

The Engineering and Mining Journal, New York,
1916, vol. cii, pp. 621-624.
215

BIBLIOGRAPHY

M. de Lummen. " The Roasting of Blende," The Chemical Trade
Journal and Chemical Engineer, London, 1916, vol. Iviii,
pp. 255-257. Also 1916, vol. lix, pp. 261-262.

H. C. H. Carpenter. " The Future of the Zinc Smelting Industry
in Great Britain," Nature, 1916, vol. xcviii, pp. 129-

131-

W. T. Flanders. "Galvanizing and Tinning," New York and
London, 1916.

G. C. Stone. " Spelter : Its Grades and Uses," Report of the
Committee on Non-Ferrous Metals and Alloys to the
American Society for Testing Materials, 1917.

H. M. Ridge. " The Utilisation of the Sulphur Contents of Zinc
Ore," Journal of the Society of Chemical Industry,
1917, vol. xxxvi, pp. 676-684.

J. H. Hastings. " Sampling and Analysing Zinc Ore and Pro-
ducts," The Engineering and Mining Journal, New
York, 1917, vol. civ, pp. 163-165.

R. G. Hall. " Some Economic Factors in the Production of
Electrolytic Zinc," Bulletin No. 129, The American
Institute of Mining Engineers, New York, September,
1917, pp. 1287-1302.

G. C. Stone. " Oxide of Zinc," Bulletin No. 129, The American
Institute of Mining Engineers, New York, September,
1917, pp. 1217-1228.

W. J. Sharwood. " Zinc Dust as a Precipitant in the Cyanide
Process," Bulletin No. 129, The American Institute of
Mining Engineers, New York, September, 1917, pp. 1303-

W. R. Ingalls. " Zinc Burning as a Metallurgical Process,"

Bulletin No. 129, The American Institute of Mining

Engineers, September, 1917, pp. 1229-1234.
C. P. Fiske. " Palmerton Zinc Refractories," Bulletin No. 130,

The American Institute of Mining Engineers, New York,

October, 1917, pp. 1719-1738.
E. M. Johnson. " Zinc Furnace Temperatures," Metallurgical

and Chemical Engineering, New York, 1917, vol. xvii,

pp. 300-302.
L. E. Wemple. " Zinc Refining," The American Institute of

Mining Engineers, New York, 1917.
" The Chemistry and Metallurgy of Zinc," American.

Chemical Society, 1917.
216

BIBLIOGRAPHY

L. E. Wemple. " The British Spelter Industry/' Engineering,

1918, vol. cv, pp. 167-169, 200—204.
Zinc-Ores. (Imperial Institute Monographs on Mineral Resources,

with special reference to those of the British Empire) .

London, 1918.
- Report of the Departmental Committee on Sulphuric

Acid and Fertiliser Trades, London, 1918 [Cd. 8994].

(Contains references to Sulphur from Zinc Blende

Roasting.)

r ./ " -• v r '"** _ " •' "^

Zinc Alloys : Brasses.

G. Guillemin. " Sur la metallographie microscopique des
alliages du cuivre " (Rapport presente a la Commission
des methodes d'essai des materiaux de construction le
5 Avril 1893 ; vol. ii, des travaux de la dite Commission,
pp. 19-25).

G. Charpy. " Recherches sur la alliages de cuivre et de zinc,"
Bulletin de la Societe d'Encouragement (5° Serie),
Fevrier, 1896, vol. i, p. 180.

W. C. Roberts-Austen. "The Copper-Zinc Series of Alloys,
known as the Brasses" (Fourth Report to the Alloys
Research Committee of the Institution of Mechanical
Engineers, 1897).

Sperry. " The Influence of Lead on Rolled and Drawn Brass,"
Transactions of the American Institute of Mining
Engineers, 1898, vol. xxvii, p. 485.

E. S. Shepherd. " Constitution of Copper-Zinc Alloys," Journal

of Physical Chemistry, June, 1904, vol. viii, pp. 421-435.

O. F. Hudson. " Micro-structure of Brass," Journal of Society

of Chemical Industry, 1906, vol. xxv, pp. 503-505.
W. J. Davis. " A Short History of the Brass Trade," London,

1908.

E. A. Lewis. " Heat Treatment of Brass and Bronze," Journal
of Society of Chemical Industry, 1908, vol. xxvii,
pp. 479-481.

G. D. Bengough and O. F. Hudson. " Heat Treatment of
Copper-Zinc Alloys," Journal of Society of Chemical
Industry, 1908, vol. xxvii, pp. 43-52.

G. D. Bengough and O. F. Hudson. " The Mechanism of Anneal-
ing in the Case of Certain Copper Alloys," Journal of
Institute of Metals, 1909, vol. i, pp. 89-124.
217

BIBLIOGRAPHY

J. T. Milton. " Some Points of Interest concerning Copper and
Copper Alloys," Journal of Institute of Metals, 1909,
vol. i, pp. 57-88.

E. L. Rhead. " Notes on Some Probable Causes of the Corrosion

of Copper and Brass," Journal of Institute of Metals,

1909, vol. ii, pp. 73-97.
T. Turner and M. T. Murray. " The Copper-Zinc Alloys : A

Study of Volume Changes," Journal of Institute of

Metals, 1909, vol. ii, pp. 98-150.
G. D. Bengough and O. F. Hudson. " The Heat Treatment of

Brass," Journal of Institute of Metals, 1910, vol. iv,

pp. 92-127.
H. S. Primrose. " Metallography as an Aid to the Brassfounder, ' '

Journal of Institute of Metals, 1910, vol. iv, pp. 248—264.
H. C. H. Carpenter and C. A. Edwards. " A New Critical Point

in Copper-Zinc Alloys : Its Interpretation and Influence

on their Properties," Journal of Institute of Metals,

1911, vol. v, pp. 127-193.
P. T. Bruhl. " The Corrosion of Brass, with Special Reference

to Condenser Tubes," Journal of Institute of Metals,

1911, vol. vi, pp. 279-311.

Norsa. " Electrical Properties of Copper-Zinc Alloys," Compt.

rend., 1912, vol. civ.
H. C. H. Carpenter. " Further Experiments on the Critical

Point at 470° C. in Copper-Zinc Alloys," Journal of

Institute of Metals, 1912, vol. vii, pp. 70—104.
G. D. Bengough. " A Study of the Properties of Alloys at High

Temperatures," Journal of Institute of Metals, 1912,

vol. vii, pp. 123-190.

F. Johnson. " The Influence of Tin and Lead on the Micro-

structure of Brass," Journal of Institute of Metals, 1912,
vol. vii, pp. 201-217.

H. C. H. Carpenter. " The Structural Resolution of the Pure
Copper-Zinc ^-Constituent into o + y," Journal of
Institute of Metals, 1912, vol. viii, pp. 51-58.

" The Effect of other Metals on the Structure

of the /3-Constituent in Copper-Zinc Alloys,"
Journal of Institute of Metals, 1912, vol. viii, pp.

59-85.
T. Turner. " Oxygen in Brass," Journal of Institute of Metals,

1912, vol. viii, pp. 248-257.

218

BIBLIOGRAPHY

C. H. Desch and S. Whyte. " The Micro-Chemistry of Corrosion.

Part I. Some Copper-Zinc Alloys," Journal of Insti-
tute of Metals, 1913, vol. x, pp. 304-328.

Gillett. " Brass Furnace Practice in the United States," New
York, 1914.

J. E. Stead and H. G. A. Stedman. " Muntz Metal : The
Correlation of Composition, Structure, Heat Treatment,
Mechanical Properties, &c./' Journal of Institute of
Metals, 1914, vol. xi, pp. 119-150.

R. J. Dunn and O. F. Hudson." Vanadium in Brass : The Effect
of Vanadium on the Constitution of Brass containing
50-60 per cent, of Copper," Journal of Institute of Metals,
1914, vol. xi, pp. 151-168.

S. Whyte and C. H. Desch. " The Micro-Chemistry of Corrosion.
Part II. Thea-Alloys of Copper and Zinc," Journal of
Institute of Metals, 1914, vol. xi, pp. 235-251.

O. F. Hudson. " The Critical Point at 460° C. in Zinc-Copper
Alloys," Journal of Institute of Metals, 1914, vol. xii,
pp. 89-110.

F. Johnson. " A Note on the Annealing of Brass," Journal of
Institute of Metals, 1914, vol. xii, pp. 111-115.

W. E. Thorneycroft and T. Turner. " Behaviour of Copper-Zinc
Alloys when Heated in a Vacuum," Journal of Institute
of Metals, 1914, vol. xii, pp. 214-229.

S. Whyte. " The Micro-Chemistry of Corrosion. Part III.
The a/3- Alloys of Copper and Zinc," Journal of Institute
of Metals, 1915, vol. xiii, pp. 80-99.

O. F. Hudson and R. M. Jones. " The Constitution of Brasses
containing Small Percentages of Tin : A Contribution
to the Ternary System Copper-Zinc-Tin," Journal of
Institute of Metals, 1915, vol. xiv, pp. 98-115.

D. Meneghini. " Structural Changes in Industrial Brasses,"

Journal of Institute of Metals, 1915, vol. xiv, pp. 154-

159-
" The Hardness of Copper-Zinc Alloys," Journal of

Institute of Metals, 1915, vol. xiv, pp. 160-167.
S. L. Hoyt. " The Grey Constituent which forms by adding Tin
to the Brasses," Journal of Institute of Metals, 1915,
vol. xiv, p. 188.

219

BIBLIOGRAPHY

C. H. Mathewson and E. M. Thalheimer. " The Annealing of
Arsenical Brass containing 61 and 62-5 per cent, of
Copper : A Study of the Structure and Properties
developed by Varying the Rate of Cooling within the
Transformation Range/' Journal of Institute of Metals,
1916, vol. xvi, pp. 18-83.

C. H. Mathewson and A. Philips. "The Recrystallization of
tf-brass after Cold-working," Bulletin of the American
Institute of Mining Engineers, 1916, p. I.

P. D. Merica and R. W. Woodward. " The Failure of Brass. I.
Microstructure and Initial Stress in Wrought Brasses of
the Type Copper 60, Zinc 40 per Cent/' United
States Bureau of Standards, Technical Paper No. 82,
1916.

O. W. Ellis. " The General Properties of Stampings and Chill
Castings in Brass of approximately 60 : 40 Composi-
tion/' Journal of Institute of Metals, 1917, vol. xvii,
pp. 25-43.

" Note on the Machining Properties of Brass,"

Journal of Institute of Metals, 1917, vol. xvii, pp. 44-64.

H. M. Thornton and H. Hartley. " The Melting of Brass and
Copper in a Crucible Furnace with Coal-gas Fuel,"
Journal of Institute of Metals, 1917, vol. xvii, pp. 213-230.

R. A. Wood. " Brass Rolling Mill Alloys," Journal of American
Institute of Metals, 1917, vol. xi, pp. 181-192.

O. Smalley. " The Influence of Arsenic on Brass," Journal of
Society of Chemical Industry, 1917, vol. xxxvi, pp.

429-439-
H. W. Brownsdon. " Cartridge Brass," Journal of Society of

Chemical Industry, 1917, vol. xxxvi, pp. 794-796.
B. P. Haigh. " Experiments on the Fatigue of Brasses,"

Journal of Institute of Metals, 1917, vol. xviii, pp. 55-86.
O. W. Ellis. " A Comparison Screen for Brass," Journal of

Institute of Metals, 1917, vol. xviii, p. 171.
L. C. Harvey. " Fuel Economy Possibilities in Brass Melting

Furnaces," Journal of Institute of Metals, 1917, vol. xviii,

pp. 213-241.
W. R. Webster. "The Cold Working of Brass," Journal of

the American Society for Testing Materials, 1917,

vol. xvii.

230

BIBLIOGRAPHY

Zinc Alloys : Nickel-Silver (so called).

O. F. Hudson. " The Microstructure of German Silver," Journal

of Institute of Metals, 1913, vol. ix, pp. 109-119.
F. C. Thompson. " Nickel-Brass/' Transactions of the Chemical

Society, 1914, vol. cv, p. 2342.
" The Annealing of Nickel-Silver. Part I," Journal

of Institute of Metals, 1916, vol. xv, pp. 230-263.
" The Annealing of Nickel-Silver. Part II," Journal of

Institute of Metals, 1917, vol. xvii, pp. 119-140.
C. C. Karr. " The Casting of Nickel-Silver," Journal of the

American Institute of Metals, 1917.

Zinc-Aluminium and other Zinc Alloys.

E. S. Shepherd. " Aluminium-Zinc Alloys/' Journal of Physical

Chemistry, 1905, vol. ix, pp. 504-512.
W. Rosenhain and S. L. Archbutt. " The Alloys of Aluminium

and Zinc," Journal of Institute of Metals, 1911, vol. vi,

pp. 236-258.
" The Alloys of Aluminium and Zinc" (Tenth Report of

the Alloys Research Committee of the Institution of

Mechanical Engineers. Collected Researches of the

National Physical Laboratory), 1913, vol.x, pp. 1-90.

E. F. Lake. " Zinc-base Alloys used for Die-moulded Castings/'

Mechanical World, 1914, vol. Ivi, p. 64.
O. Bauer and O. Vogel. " Aluminium-Zinc Alloys," International

Journal of Metallography, 1916, vol. viii, p. 101.

221

INDEX

Aich's metal, 179
Alloys of zinc, 173, 190
Aluminium and zinc, 187
American zinc industry, 14, 40, 106
Annealing of zinc, 138, 143
Anti-friction metals, 185
Australian concentrates, 29, 99, 208

Belgian zinc industry, u, 37
Bibliography : alloys of zinc, 217

metallurgy of zinc, 213
Blue powder, 171
Brass, constitution, 175

early production, 7

history of, 7, 174

industrial, 175

Brasses, composition of, 175, 190
British zinc industry, 10, 18, 106, 198
British zinc works, 28
By-products, in

Cadmium, 118, 146
Calamine brass, 7, 175
Calcination, 79
Casting of zinc, 139, 167
Chamber process, 112
Charging machine, 105
Chemical properties of zinc, 137
Complex zinc ores, 70, 109
Compounds of zinc, 191
Condensers, 95
Consumption of zinc, 157

world's, 1 60
Contact process, 112
Convention, 2, 155
Cost of zinc production, 119

Delta metal, 179
Die-casting, 186
Distillation, methods of, 94
process, 92

Electric smelting of zinc, 1 24
Electro-deposition of zinc, 131, 137
Etching reagents for zinc, 142
Europe : production of zinc, 159
of zinc ore, 56

Filters, 102

Fine zinc, 6

" Flotation," 72

" Flux skimmings," 163

Fracture of zinc, 137

Fume, 118

Furnace, distillation, 95

Furnaces, Delplace, 84

electric, 124

Hegeler, 87

Merton, 90

Ridge, 90
Future of zinc industry, 198

Galvanising, 14, 161

centres, 161
" German silver," 182
German zinc industry, n, 33
Grades of zinc, 6, 103, 148
Granulated zinc, 138

Hardness of zinc, 137
Hard zinc, 181
History of zinc, 7
Hydro-metallurgical processes, 130

Imports of zinc, 26

of zinc ore, 26
Impurities in zinc, 145
Industrial applications, 161
Iron and zinc, 181

Labour in zinc works, 18, 122
Lead in zinc, 102, 145
Liquation, 102, 146

INDEX

Lithopone, 193
Losses in smelting, 101

Malleability of zinc, 137
Melting point of zinc, 139
Microphotographs of brass, 144

of zinc, 143

Micro-structure of zinc, 140
Miscellaneous zinc alloys, 189
Muffle furnaces, 84, in

" Nickel-silver," 182
Non-ferrous Metals Bill, 2

Ores of zinc, 46
America, 61
Australia, 53
Belgium, 57
China, 68

concentration of, 70
France, 57
Germany, 58
Greece, 59
India, 54
Italy, 60
Japan, 68
marketing of, 70
roasting of, 81
Russia, 60
Siberia, 69
Spain, 60
Sweden, 61
Tasmania, 54, 134
United Kingdom, 51
valuation of, 73

Physical properties of zinc, 137
Pigments, 191, 195
Price of zinc, 3, 151
Production of zinc, America, 41

Belgium, 37

British, 20

China, 8, 43

France, 38

Germany, 34

Holland, 38

Japan, 44

Norway and Sweden, 39

Russia, 39

World's, 15, 1 6

Re-distillation, 103
Reduction and distillation, 92
Refining, 102
Residues from retorts, n8, 119

Retorts, graphite, 103

manufacture of, 96

types of, 95

vertical, 108
Roasting, 81

furnaces, classified, 83
Rolled zinc, 13, 138, 166

Sampling zinc, 150

zinc ore, 77
Schoop's process, 165
Sheet zinc, 13, 138, 166
Sherardising, 164
Silver in zinc ores, 75
Silver-zinc alloys, 189
Smelting losses, 101
Solubility of zinc, 140
Spelter, definition, 5, 8
Sterro-metal, 179
Sulphur fumes, 84, in
Sulphuric acid, in, 207

Tensile strength of zinc, 138
Typical zinc alloys, 190

United States, zinc production, 41,

158
zinc ore production, 62

Wet methods, 130

World's consumption of zinc, 160

World's production of zinc, 16, 158

zinc ore, 56
World's zinc markets, 154

Zinc alloys, composition, 190
Zinc castings, 167
Zinc chloride, 195
Zinc Convention, 2, 155
Zinc dust, 97, 100
Zinc-lead pigment, 195
Zinc ore trade, 77
Zinc oxide, 139, 191

reduction of, 93, 99
Zinc smelting centres, 18, 28, 34, 37,

38>4i
Zinc smelting in America, 40

Australia, 29, 99

Belgium, n, 37

blast furnace, 108

Canada, 31

Germany, 33

Great Britain, 18, 198

Tasmania, 31, 134
Zinc sulphate, 197
Zinc white, 191

223

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